Image copyright PA Image caption Conservative Party chairman Brandon Lewis was criticised for breaking an agreement with an MP on maternity leave

The Conservatives have committed to ensuring half of their Parliamentary candidates are female.

Tory chairman Brandon Lewis said he wanted his to be the "party of equal opportunity" and to remove barriers preventing women from participating.

He said women had "all too often" been excluded from having a voice.

Mr Lewis was criticised last month for breaking an agreement allowing Lib Dem MP Jo Swinson, who was on maternity leave, to miss a key Brexit vote.

He was supposed to abstain in the crunch votes on the government's Trade Bill so Ms Swinson's absence would not count against her side - but registered his vote anyway.

The Tories apologised and said it was an "honest mistake" - and Mr Lewis addressed the row in his speech, saying voting while on parental leave presented a "particular challenge" for MPs.

He said he had not known he was paired with Ms Swinson, but that "when mistakes are made it's not good enough".

Ms Swinson responded on Twitter to his speech, which was titled The Voice of Women in Politics, with a laughing emoji:

Women currently make up 21% of Conservative MPs, compared to 45% for Labour, which has all-women shortlists for parliamentary candidates in some seats.

A proposal last year by the Commons Women and Equalities Committee to set a 45% female representation target for Parliament and local councils was rejected by the government, which said parties should take the lead.

Mr Lewis said achieving the "ambition" of 50% of candidates being female would not be easy, but pledged to "work tirelessly to make this a reality".

About 40% of Tory members are women, he said.

He said women took longer than men to apply for a shortlist once they have expressed an interest, saying he did not know why this was and promising to commission a "substantial piece of research into the issues that lead women away from political and public life".

He said: "We will use this to take action to break down barriers wherever they exist, and provide the practical steps to overcome them."

Image copyright PA Image caption Jo Swinson responded to Mr Lewis's remarks with a series of emojis

Speaking to BBC Radio 4's Woman's Hour, Mr Lewis said the Tories would not be operating all-women shortlists for candidates.

"In terms of quotas and shortlists, I think that just masks the underlying problems within organisations," he said.

"We need to change the culture across our political landscape, get that systemic change, not just a short-term fix."

The Equality and Human Rights Commission has called for it to be mandatory for political parties to report details of the diversity of their candidates.

Ben Wilson, the commission's executive director, said the Tories' announcements were "a positive step towards achieving gender equality in politics".

"To bring about real change the government must identify and remove barriers to women's participation in politics including the intimidation of female parliamentarians and issues around parental leave and flexible working," he added.