Labour’s deputy Leader has said “things have to change” in the wake of the party’s devastating by-election defeat in Copeland.

Tom Watson reminded his party it must win 100 seats at the next election to overthrow the Tories and that holding on to constituencies like Copeland should be “the easy bit”.

He demanded Labour reconnect with its natural voters and pursue a “broad” agenda that could unite people from different backgrounds, including those who “create prosperity”.

While the Deputy Leader said it was “not the time” for another leadership election, his words will be read by some as a criticism of the approach adopted by Jeremy Corbyn up to now.

It comes after ex-foreign secretary David Miliband also used an interview to signal a potential return to UK politics and advocate a return for Labour to a centre-left pro-European agenda.

Labour’s shocking by-election loss to the Tories in Copeland, the first time an opposition party has lost a by-election to a governing party in decades, left one member of Mr Corbyn’s own frontbench admitting the result would deliver Labour’s worst general election result since the 1930s if replicated in 2020.

Seeking to regain the initiative in the wake of the result, Mr Watson said: “I’m hugely disappointed that Gillian Troughton won’t be joining [Labour] in Parliament as the MP for Copeland.

“That means that all of us with leadership roles in the Labour Party need to have a long, hard look at ourselves and what’s not working. Seven years into a Tory government, we shouldn’t be facing questions about whether we can retain the seats we already hold.

“Our job at the next election is to gain over 100 seats. Keeping what we have is supposed to be the easy bit.”

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While stating that the issue of the leadership was settled last year, he added: “We have to do better. We cannot sustain this level of distance from the electorate, from our natural supporters. So things have to change.”

He cited one of the latest opinion polls suggesting Labour is five and half million votes behind Theresa May’s Tories.

Apparently taking on claims by Mr Corbyn’s supporters that Labour is progressing because of the size of its membership, Mr Watson said: “We pride ourselves on being the biggest mass-membership political party in Europe, with more than half a million members. That’s great.

“But five and a half million votes is ten Labour Parties. So we have to reach out.

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“We've won in our own right before by appealing across the country, to Tories and SNP voters – to Lib Dems, UKIP supporters and Greens. By persuading them to change their minds and switch their votes.”

Mr Watson argued that the party had to make it clear that it is on the side of people “who create prosperity” as well as those who need job security, before later repeating that Labour should be “unafraid to talk about prosperity, and about supporting business.”

He also pointed to greater devolution to regions and cities as a way that the party could reach a unified approach to Brexit, whilst making demands of Ms May as she secures a deal to take the UK out of Europe.

But he dismissed the idea of forming a “progressive alliance” with other parties claiming that it is “an electoral dead end”.

In an interview with The Times on Saturday, Mr Miliband said he is “deeply concerned” over Labour's future. Asked whether he would consider a comeback, he added: “I honestly don't know what I'm going to do. It's hard to see, but what's the point of saying never?”