Image copyright AFP Image caption The MPs hope to influence the government as the negotiations play out

All options should remain on the table in Brexit negotiations, a newly formed cross-party group of MPs have claimed.

Labour's Chuka Umunna said there must be a deal which maintained the closest links with the EU, including possibly remaining in the single market.

He said it was "nonsense" to claim the group, whose members include ex-Tory minister Anna Soubry and Green leader Caroline Lucas, wanted to stop Brexit.

On Sunday, Lib Dem Vince Cable said in his view Brexit may not happen.

Parliament voted by a large margin earlier this year to begin the process of leaving the EU following last year's referendum vote. The UK is currently due to exit on 30 March 2019.

In a speech on Tuesday, Theresa May will call for cross-party co-operation in a range of areas following her failure to win a majority in the election, although it is unclear whether this offer of dialogue will extend to Brexit.

The PM's Brexit strategy envisages leaving the single market and customs union while she has insisted that although she believes a deal will be struck, she will be willing to leave without one if it what is on offer is not acceptable.

The Democratic Unionists have already pledged to support her government in Brexit votes in the Commons but, even with their backing, the prime minister only has a slim working majority of 13 and is vulnerable to any rebellions in her own party amid continuing speculation about her future.

'Decent deal'

The All-Party Parliamentary Group on EU Relations, whose other members include Lib Dem deputy leader Jo Swinson and figures from the SNP and Plaid Cymru, says its has three priorities: to ensure the UK does not exit the EU without a formal deal; to ensure that all options are kept on the table as talks progress; to ensure the "closest possible relationship" with the remaining 27 EU members after Brexit.

Mr Umunna rejected suggestions that the group effectively wanted to keep the UK in the EU in all but name, telling the BBC that although he personally favoured staying in the EU's single market and customs union, some of his colleagues had different views.

"Anna Soubry and I both voted to trigger Article 50 so all this nonsense that we want to relitigate the referendum - no we don't - or ignore the result - no we don't," he told the BBC's Daily Politics.

Image copyright AFP Image caption The launch comes ahead of the publication of the Great Repeal Bill later this week

"But what we want to do is ensure we have a decent deal for our constituents. That's why we have come together in the national interest to make it happen."

Ms Soubry has pledged to co-ordinate their efforts in Parliament to ensure a "practical not ideological" approach to Brexit talks.

Mr Umunna was criticised by senior figures in his own party after he unsuccessfully tried to amend the Queen's Speech last month to get the UK to commit to remaining in the single market and customs union.

Labour has conceded the UK will leave the EU's internal market but says the UK must maintain tariff-free access to it that will leave businesses no worse off.

The new group's launch comes ahead of the publication later this week of legislation to convert 40 years worth of EU into British law ahead of the UK's departure. The Repeal Bill is likely to be challenged by opposition parties in the Commons.

Conservative MP Rishi Sunak said the group should come clean about its intentions and said that remaining a member of the single market - and therefore having to continue accepting freedom of movement and the authority of the European Court of Justice - would be unacceptable.

"We have a clear position. We voted to leave the EU. Staying inside the single market would be a betrayal of that vote," he told Daily Politics.

"I think people would view that as very much staying inside the EU so I think we need to be clear about that. The rest of the country voted to leave and leaving means removing ourselves from those institutions."