Labour's Shadow Science Minister Chi Onwurah MP tells Business Insider: "If the choice is between a second referendum and a deal which is bad for Britain then I would go for a second referendum."

Shadow Brexit secretary Keir Starmer was in Brussels last week having talks about alternatives to Prime Minister Theresa May's Brexit deal.

Corbyn has come under increasing pressure to back a second referendum.

One of Theresa May's own ministers resigned on Friday calling for a new vote on leaving the EU.

LISBON —A shadow minister in Labour leader Jeremy Corbyn's frontbench team has joined growing calls for a second EU referendum, telling Business Insider that a second vote will be necessary if May's Brexit deal is bad for Britain.

Labour's shadow science minister Chi Onwurah told Business Insider that while she would prefer a general election, she would support a second referendum on Brexit if the deal Prime Minister Theresa May puts to parliament fails to meet the opposition's six "tests."

"If the choice is between a second referendum and a deal which is bad for Britain then I would go for a second referendum," Onwurah told BI.

"I would prefer to have a general election of course, but if the choice is a deal which the Tories have engineered so that it's going to take us into a race to the bottom, loss of workers rights, no access for my constituents, then I would back [it]," she said.

Her comments come as one of Theresa May's own ministers resigned from government, calling for a second referendum on Brexit.

The Transport minister Jo Johnson quit on Friday, saying that the Brexit decision must "go back to the people."

Onwurah previously indicated she might support a second vote during the last Labour leadership election.

However, Labour leader Jeremy Corbyn has since resisted calls to explicitly back a new vote, saying only that the party would leave "all options ... on the table" in the event that May's deal fails to pass through parliament.

Onwurah joins an increasingly loud chorus of voices demanding a second bite of the cherry on Brexit. A group of pro-Remain business leaders last week also called for a second referendum. The former head of the civil service, Bob Kerslake, who now advises the Labour leader, also joined the calls in the past week, telling Business Insider that a second vote was now needed to prevent the "catastrophe" of a no-deal Brexit.

When pressed on whether that put her at odds with Labour leader Jeremy Corbyn — who would prefer a general election and a deal that meets his six tests — she laughed.

"It's very difficult, you are asking for more certainty from the opposition who are not in government than you are from the actual government, far more."

Asked whether the country needed certainty, she replied: "Well exactly, and we are a government in waiting. That's absolutely true. So I recognise that, but we haven't got the civil service [to provide administrative support], and Keir Starmer is in Brussels today."

She added that Starmer and Corbyn have both been to Brussels to confer with EU officials on alternatives to May's Brexit.

Starmer is "seeing, talking about what kind of deal we could have. He's in Brussels — Keir's been in Brussels a lot and so has Jeremy," Onwurah said.

Read more: Polling data offers a clue to why Theresa May's own MPs have plotted against her so viciously.

Asked if that amounted to a parallel set of talks that Brussels was holding with Labour, in the event that May's Conservative government falls, she replied that: "There are talks ... I also wouldn't say that what's happening with the Tories are 'real' negotiations because you see that every time they put something forward something comes back again. ... So there are definitely, Keir and Jeremy have been talking to our European sister parties and colleagues."

Onwurah said she believed there were only about four Labour MPs — out of 257 in the 650-seat House of Commons — who were absolutely pro-Leave, and another 40 who are Remainers but represent constituencies that voted Leave, and thus might be open to backing May's deal.