Warning that the process of Brexit was "slipping away", Theresa May said that a reshaped package for securing London's departure from the EU would be put up for approval next month. "There is now one last chance," the British prime minister said. "Reject this deal and leaving the EU with a negotiated deal any time soon will be dead in the water." Outlining a series of major changes in the package, she said the government would put up a second referendum as an option to choose, even though she opposes the concept. But her colleagues would only get that chance if her Brexit bill passed the first stage of voting in parliament. The bill would also provide an obligation on governments to avoid the so-called Irish backstop that would prevent trade and tariff checks on the island. While the basic agreement on the British exit can’t be touched, a political declaration on future trade and other relationships with Brussels can be redrafted to reflect the measures in the bill. Mrs May also indicated she could make commitments on workers’ rights and environmental protections. Those issues were discussed in cross-party talks with the opposition Labour Party and politicians from both sides said some common ground was found. As the provisions could be covered by domestic legislation, the EU wouldn’t care how London resolved the issues. The measure would also offer the right to approve the government's negotiating position with the EU both before and after talks. She will also allow MPs to vote on different options for post-Brexit customs arrangements. The Withdrawal Agreement Bill would include provisions to ensure there is no need for checks on goods at the border with the EU. "The most difficult area is the question of customs," she said. "At the heart of delivering Brexit lies a tension between the strength of our ambition to seize the new opportunities that Brexit presents - and the need to protect the jobs and prosperity that are built on an interconnected relationship with other European economies." A full customs union was a key demand from Labour in cross-party talks. Mrs May said that would stop Britain being free to strike trade agreements with other countries around the world. A leading member of the Labour Party John McDonnell, the finance spokesman, said that a forthcoming change in the leadership of the Conservative Party made it difficult to back Mrs May's legislation. “Even the statement today, no matter how effusive, it’s very difficult to see how they can sustain any deal with us,” Mr McDonnell said. “Particularly when there’s a change of leadership and a number of candidates have indicated they’d tear up the new deal. “The outstanding problem is still the instability of the government, whatever they bring forward.” A Conservative Party rebellion against Mrs May's approach continues to ebb and flow with politicians who backed the withdrawal when it failed for a third time in March now pulling away from supporting the leader. During a three-hour meeting of the cabinet the most heated part of the discussion was around the idea of allowing members of Parliament a free vote on the option of holding a second Brexit referendum. There was disagreement as pro-Brexit ministers pushed back against the idea. Parliament rejected a second referendum when it last had the chance to vote on the possibility.A free vote would let MPs decide as they like on whether to hold another public vote on leaving the EU, rather than being instructed by party whips. Simon Coveney, the Irish foreign minister, warned on Tuesday that the risk of a disruptive no deal Brexit was higher than it had ever been. He said that too many were "perhaps taking the view that it is going to be alright on the night. And it may well be alright on the night but we cannot assume that". <strong>The ten points outlined by Mrs May:</strong> One - the Government will seek to conclude Alternative Arrangements to replace the backstop by December 2020, so that it never needs to be used. Two - a commitment that, should the backstop come into force, the Government will ensure that Great Britain will stay aligned with Northern Ireland. Three - the negotiating objectives and final treaties for our future relationship with the EU will have to be approved by MPs. Four - a new Workers’ Rights Bill that guarantees workers’ rights will be no less favourable than in the EU. Five - there will be no change in the level of environmental protection when we leave the EU. Six - the UK will seek as close to frictionless trade in goods with the EU as possible while outside the single market and ending free movement. Seven - we will keep up to date with EU rules for goods and agri-food products that are relevant to checks at border protecting the thousands of jobs that depend on just-in-time supply chains. Eight - the Government will bring forward a customs compromise for MPs to decide on to break the deadlock. Nine - there will be a vote for MPs on whether the deal should be subject to a referendum. And ten – there will be a legal duty to secure changes to the political declaration to reflect this new deal.