Rostowski, EU chief Donald Tusk's finance minister from 2007 to 2013, was at the helm of the Polish economy in the immediate aftermath of the global economic crisis.

Although he has, he says, no plans at present to return to front-line politics, as an ordinary party member - as he puts it - he still has many political ideas and energy. Alongside Tusk and the then foreign minister, Radoslaw Sikorski, the governing Civic Platform (PO) looked electorally invincible.

Rostowski oversaw an overhaul of the public finance sector, with a cap on spending growth and a decision to redeem sovereign bonds held by privately managed pension fund companies, which was widely criticised by economists, but he was widely seen as a reliable pair of hands.

The British-Polish politician fell in 2013 as a series of scandals rocked an otherwise steady PO boat and his party lost power in 2015 to Jaroslaw Kaczynski's populist Law and Justice (PiS) government.

The ratings agencies and markets more widely warned in the first half of 2016 that PiS's policies of taxing banks, supermarkets and other Western controlled entities would make it harder for Warsaw to keep its budget in balance, would add to borrowing costs and drive down its currency. Unemployment and inflation would rise.

None of these things have happened since the end of 2015, when PiS unveiled policies to ‘repolonise' Polish business and hand out 500 zlotys per child to larger families.

So, with elections in 2019, what kind of opposition is there to the governing party and what would it do if it regained power?

What goes around, comes around

Rostowski starts off by attacking PiS's economic results. "PiS has also overseen terrible macroeconomic results. Only 2.5 percent growth in 2016 is in effect a massive slowdown and puts Poland's public finances in danger," he says.

"This was directly due to the investment slowdown. Investment in fact fell off a cliff, with investors afraid and this was directly related to the assault on the rule of law and due process. Given the growth in the EU, Poland should have seen 4 percent growth, as it did in 2015, when European growth was slower."

"PiS does not have economic policies, they are all political," he goes on. "They do represent demographic policy changes which to some extent are positive, but the purpose is entirely political. This has economically very risky ramifications, a failure in particular to cut the public sector deficit, creating no buffer. They have individual projects, but no overall macroeconomic policy. They are simply not very good at doing policy and look very unhappy doing it. [Finance Minister Mateusz] Morawiecki is absolutely pathetic."

But Rostowski also suggests that PiS' center-left keynote policies might stay. "We do not want to reverse PiS changes, for example, in pensionable age and extend the 500+ program to the first child."

PiS two-faced

"I would distinguish between the populism of aggression and economic populism. PiS pretended to be less aggressive than it really was and more economically populist," Rostowski says.

"They hid [defense minister Antoni] Macierwicz and [party leader Jaroslaw] Kaczynski, both of whom have massive negative approval ratings, from the limelight. Duda and Szydlo were presented as the true fan, a fresher faced, pleasant young man and a  motherly middle-aged woman. People voted for a better version of PO and got a worse version of PiS."

"Both have proved to be spineless, unable to stand up to Kaczynski and fulfill the obligations of their office, repeatedly breaking the law and the constitution at his behest."

KOD peaked

Rostowski belives, he said, that support for the Committee for the Defence of Democracy (KOD), a social media-led anti government protest movement - is waning. Its leader, Mateusz Kijowski, was ousted in fact later in the day of the interview.  

"It is parties, not social movements, that will fight the next election in 2019. We can cooperate with KOD, but we don't need to make that our only focus,” he said. 

"Shortly after an election civil protest, demonstrations, etc. are naturally the preferred form of opposition to a govt. that keeps breaking the law and the constitution, but as the election draws closer opposition parties naturally become more important in the struggle." 

Popular Front

Asked if PO might enter a broad anti-PiS united front, Rostowski said: "PO has said clearly that this is its intention, and if PiS changes the voting system to single member constituencies, this will be absolutely essential."

Such a formation might need to also include the left, "who claim they are defenders of democracy,” he says.

"Populism breeds anti-populism and there is a highly integrated, very angry electorate out there for the taking. Remember, a majority are anti-PiS.”

Rostowski nods to the power of PiS centre-left keynote policies. "We do not want to reverse PiS changes, for example, in pensionable age and extend the 500+ program to the first child."

How did PiS win? 

"PiS was also very lucky, with the collapse of the left. It the left had breached 8 percent PiS would have had to have a coalition with Kukiz, and he is unlikely to have agreed."

"PiS has no respect for the constitution. There was no landslide, that is my point. PiS won 37.5 percent and gained 235 seats (an absolute majority in the Sejm) PO, won 42 percent in 2011 and obtained 208 seats, well short of a majority."

"Kaczynski great skill was in bringing together socially center-right and economically centre-left. But PiS is 30 percent, its hardcore, which we wont break into. The other 7-8 percent is for the taking. There is no long-term trend in Polish society towards authoritarianism, in fact it is the other way around."

"Poland was first into this populist cycle and I hope also therefore it will be the first out," Rostowski says. "PiS was a pregenitor of the populist trend, but had to pretend to be less populist than it really was.”