“Closer alignment with the single market means handing over our hard-won sovereignty and accepting freedom of movement. That would shatter yet another Labour election pledge and betray the millions who voted to take back control of our borders.

“Why would we want to get closer to a failing EU economic model where Germany is in recession?”

The Prime Minister on Sunday insisted Britain should “go further” in strengthening post-Brexit ties with Brussels.

But he appeared to pour cold water on suggestions that the UK should re-join a customs union with the EU, despite his Health Secretary Wes Streeting saying the arrangement had “enormous economic benefits”.

Speaking to the BBC’s Sunday With Laura Kuenssberg show, the Prime Minister pointed to steps taken to align with the EU more closely on agriculture and food, adding: “That’s the sovereign decision that we have taken.

“I think we should get closer, and if it’s in our national interest to have even closer alignment with the single market, then we should consider that, we should go that far.”

Sir Keir added: “I think it’s in our national interest to go further.

“What I would say about the customs union is that I argued for a customs union for many years with the EU, but a lot of water has now gone under the bridge.

“I do understand why people are saying, ‘Wouldn’t it be better to go to the customs union?’ I actually think that now we’ve done deals with the US, which are in our national interest, now we’ve done deals with India, which are in our national interest, we are better looking to the single market rather than the customs union for our further alignment.”

But the Prime Minister insisted freedom of movement – a core principle of the EU single market – was off the table as he faced questions about what concessions he was willing to offer in return.

Asked whether he was prepared to allow EU citizens with no limit to come to the UK, he said: “No.

“But we are looking at a youth mobility scheme which will be for young people to travel, to work, to enjoy themselves in different European countries, to have that experience.”

Sir Keir has recently faced pressure from his own backbenchers to change course on a customs union, with some 13 Labour MPs backing proposals that would pave the way for such an arrangement in a Commons vote last month.

Downing Street stated later in December that the Government will adhere to its “red lines” on the EU relationship, which include not rejoining the single market, the customs union, or reverting to freedom of movement.

However, the Liberal Democrats plan to table an amendment to the upcoming legislation that would impose a legal duty on the Government to initiate negotiations on a customs union with the EU, in an effort to force a fresh vote on the issue.