British MPs have steered key Brexit legislation through its first Commons test amid growing Tory unrest over setting an exit date in law.

The government comfortably navigated two votes on the European Union (Withdrawal) Bill, which seeks to transfer European law into British law, during the first group of amendments.

But debate focused on the government's desire to include an exit date in the Bill of 11pm on 29 March 2019, with Tory backbenchers lining up to voice concerns.

Brexit Secretary David Davis earlier said any deal on citizens' rights, the so-called divorce bill and a transition period will only hold if MPs and peers approve a new piece of legislation to put it into British law.

But he confirmed that if the proposed Withdrawal Agreement and Implementation Bill is voted down by MPs, the UK will still leave the EU on 29 March 2019, without a deal.

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Potential Tory rebels who want a vote on the Brexit deal have suggested Mr Davis's concession may not be enough if the Government succeeds in changing the Bill to state that the UK's membership of the EU formally ends at 11pm GMT on 29 March 2019.

Yesterday, Theresa May acknowledged the "challenges" of Brexit, admitting there will be "ups and downs" but urging business leaders at the Lord Mayor's Banquet in the City of London to "embrace this period with confidence and optimism".

"Not grounded in some article of faith, but with a clear understanding of our strengths as a nation," she added.