The report, published by Parliament's Intelligence and Security Committee on Thursday, showed that women make up 37 percent of staff at domestic spy agency MI5, overseas intelligence service MI6 and signals spy agency GCHQ.

But among senior staff that number falls to just 19 percent.

This is in comparison to the civil service, where women make up more than half of the workforce.

The report places the blame on middle management, who it says some people call "the permafrost."

Lawmaker Hazel Blears, who led the review, said this group's mentality can lead to "a management culture which rewards those who speak loudest or are aggressive in pursuing their career and does not fully recognize the value of a more consultative, collaborative approach."

She said she believes these "cultural and behavioral issues" make it difficult for women to advance into more senior positions.

The document urged the agencies to provide women with career advice to help them reach their full potential, as well as enable them to organize their own informal support networks.

Women who have children and can't take on operational roles any longer shouldn't be "sidelined," it said, but instead have their skills put to use in other tasks.

Blears said having a more diverse workplace would help national intelligence-gathering services to work more efficiently, as well as provide a better work environment.

"If all intelligence professionals are cut from the same cloth, sharing similar backgrounds and similar characteristics, then they are likely to share 'unacknowledged biases,'" she said.

"Diversity will therefore result in better intelligence analysis and a better response to the range of threats that we face to our national security."

Operation: middle-aged moms

The report also encouraged Britain's intelligence services to approach women through online channels such as the popular parenting forum "Mumsnet."

It recommended recruiters not discount women just because of their age or career status.

"Women or mothers in middle-age or mid-career have valuable life experience and may offer an untapped recruitment pool," the report stated.

The push to recruit women comes after a story on the lives of female workers at French foreign intelligence service, DGSE, was featured in a magazine, in a move designed to entice female recruits.

Female spies make up just 26 percent of France's force.

This number pales in comparison to the United States' Central Intelligence Agency, where 48 percent of its staff are women.

MI5 has had two female bosses in its history.

an/sms (AP, AFP, Reuters)