Liberal Leader Justin Trudeau, faced with an open letter from seven former Liberal MPs denouncing him for his stance on abortion, tweeted that the days "when old men get to decide what a woman does with her body are long gone."

The seven former MPs said in an open letter Thursday that Trudeau is violating the spirit of the Charter of Rights and Freedoms by asking new Liberal candidates to state their views on abortion and requiring anyone with anti-abortion views to agree to "vote pro-choice" on any bills. Sitting MPs would also have to agree to vote along party lines.

"How can such a discriminatory policy serve the democratic ideals of our great nation?" wrote the ex-MPs, many of whom are known for being outspoken on socially conservative issues.

Trudeau has attempted to brand himself as a champion of openness and transparency, including committing to an open nomination process for prospective candidates in the next election. The ex-MPs who signed the letter say Trudeau's abortion policy shows he isn't respecting that promise.

"My hope is that this will generate debate about what we expect from our members of Parliament. Are they merely parrots who repeat what the leader says or are they people who can take positions that they think are in the best interests of the country?" said Tom Wappel, former Liberal MP for Scarborough-Southwest and one of the letter writers.

Wappel is an adviser to the anti-abortion group Campaign Life Coalition and has publicly opposed same-sex marriage. He said he worries a similar policy could eventually be applied to other issues such as euthanasia and human cloning.

Party 'will not back down'

Trudeau tweeted his apparent response late Thursday.

The days when old men get to decide what a woman does with her body are long gone. Times have changed for the better. <a href="https://twitter.com/hashtag/LPC?src=hash">#LPC</a> defends rights. —@JustinTrudeau

The letter was signed by Wappel, Garnet Bloomfield, Murray Calder, Rex Crawford, Pat O'Brien, John O'Reilly and Janko Peric.

In 1982, Bloomfield voted against adopting the Charter of Rights and Freedoms because of his anti-abortion views. O'Brien quit the Liberal caucus in 2005 in protest over the party's plans to legalize gay marriage.

The Liberal Party said earlier Thursday it will continue to stand by the policy.

"Anyone is entitled to hold their own personal views, but Canadians deserve to know that when they vote Liberal they will get an MP who will vote to defend women's rights in the House," party spokeswoman Kate Purchase said in a statement.

"Women's rights are long-held Liberal values that we will not back down from."