LONDON (Reuters) - Mrs Theresa May used her first parliamentary grilling as Britain's new prime minister on Wednesday (July 20) to taunt the opposition over women's' rights, pointing out that it was her party that had made her the country's second female leader after Margaret Thatcher.

After a week of many firsts, Mrs May made her most closely watched debut, taking to the floor in Parliament to lead the combative centrepiece of the British political week: Prime Minister's Questions.

She won loud cheers from the Conservative Party benches in the debating chamber as she stood to face the daunting array of questions usually levelled at the prime minister during the 30-minute grilling, which can range from major foreign policy issues to parochial affairs.

Mrs May was appointed to Britain's top job a week ago after former prime minister David Cameron resigned following the country's vote to quit the European Union, leaving her the difficult task of uniting the Conservative party and negotiating an exit from the bloc.

Mrs May, who styles herself as a down-to-earth, unflashy leader, kicked off her remarks in the house by welcoming a drop in unemployment and setting out plans to visit German Chancellor Angela Merkel and French President Francois Hollande.

But she also picked up where Mr Cameron left off last week, laying into the opposition Labour Party, whose leader Jeremy Corbyn is locked in a bitter internal power struggle in which the only female candidate to replace him dropped out on Tuesday.

"In my years here in this house I've long heard the Labour Party asking what the Conservative Party does for women, well it just keeps making us prime minister!," she said, to huge cheers from her own party as her husband looked on from the public gallery.

She added: "The Labour Party may be about to spend several months fighting and tearing itself apart. The Conservative Party will be spending those months bringing this country back together."

Mrs May said the government would ensure that it gets controls on free movement from the European Union in negotiations with the bloc following last month's Bexit vote.

"I am very clear that the vote that was taken in this country on 23 June sent a very clear message about immigration - that people want control of free movement from the European Union and that is precisely what we will be doing and ensuring that we get in the negotiations," she told Parliament.

"I also remain absolutely firm in my belief that we need to bring net migration down to sustainable levels; the government believes that is tens of thousands.

She added: "It will take some time to get there but of course now we have the added aspect of those controls that we can bring in relation to people moving from the European Union."

She also said she would set out Britain's negotiating position over the coming weeks and months.

A spokesman for German Chancellor Angela Merkel said there will be no pre-negotiations on Britain's terms for exiting the European Union during talks between Dr Merkel and Mrs May.

"When we say, and the German and European positions are similar, that there could be no pre-negotiations with Britain before Britain has officially activated Article 50, that doesn't mean that we can't talk to each other," Mr Steffen Seibert said during a regular government news conference on Wednesday. "But there are no pre-negotiations. You can be sure about that."

Mrs May also said that the government's position on the possible expansion of London's Heathrow airport had not changed, and that it would be making a decision "in due course".

"On Heathrow, the position has not changed," she told Parliament. "Obviously the Howard Davies review work was done, some further work is being done in relation to the question of air quality around the various proposals that were put forward, and the Cabinet and government will be taking a decision on this in the proper way in due course."

Often the only taste of parliamentary business that members of the public regularly get, the box-office drama known colloquially as PMQs is seen as a barometer of how well party leaders are doing and they are known to spend hours preparing.

Former Conservative leader Iain Duncan Smith on Wednesday told ITV the session was "the single most nerve-wracking thing you'll ever do in your life".

Mr Cameron made his final appearance at PMQS last week with a relaxed and jokey performance that focused on mocking Mr Corbyn and defining his legacy, before receiving a standing ovation as he left the chamber.