Jeremy Corbyn is facing further pressure to his position on Brexit after 18 more Labour MPs signed a letter calling for a second referendum.
The group of London politicians joined forces with Lib Dem leader Sir Vince Cable and two of his MPs to warn of the dangers the capital faces when the UK leaves the European Union.
The signatories of the letter to the Independent, which urged a deal that keeps Britain in the customs union and single market, included six former shadow ministers, several of whom were in place until last year.
Among the 18 are regular Corbyn critics Mike Gapes and Wes Streeting, as well as Rushanara Ali, Margaret Hodge, David Lammy and Tulip Siddiq.
They represent a third of the 49 Labour MPs in London.
It comes the day after 10 Welsh Labour MPs called for a second referendum, including Anna McMorrin and Tonia Antoniazzi, who are parliamentary private secretaries to shadow cabinet members.
Corbyn has repeatedly said Labour does not support a second national poll and fired Owen Smith as shadow Northern Ireland secretary for proposing one.
In the letter to the Independent on Saturday, the London MPs warned that the capital ‘represents all the most positive elements of being global, outward-looking, welcoming and tolerant, but that was all at risk if Brexit went badly’.
They added: ‘The Government has a mandate to negotiate a Brexit deal.
‘What the Government absolutely does not have is a mandate to force a bad Brexit deal on our city that could damage London for generations to come.
‘So much of the economy of London relies on being in the single market and the customs union, and on freedom of movement.
‘From the tech sector to finance, from construction to culture, London benefits hugely from being part of a larger European market. Outside of this European market, our city will suffer.’
Other Labour backbenchers who have called for a second referendum on the Brexit deal include MPs in the North East.