Conservatives working in the voluntary sector are reluctant to admit to party membership because they believe they will face discrimination, Conservative MP Penny Mordaunt said yesterday at her party's conference.

Mordaunt, MP for Portsmouth North and a former director at Diabetes UK with responsibility for campaigning, said: "There are people in the sector who have faced quite unpleasant discrimination for being Conservative. That's just completely wrong."

Mordaunt was speaking along with several other Conservative MPs at the launch of the Blue Book of the Voluntary Sector, a collection of essays about charities by Conservative MPs and other senior figures in the party, published by the Charities Aid Foundation and Acevo.

Her husband, Ian Lyon, said at the same event that there was a Labour bias to the sector. He said that "whenever Labour lose power they populate the voluntary sector in a very annoying way".

However several MPs disagreed, saying that volunteers in particular tended to come from social groups which predominantly voted Conservative.