Five Labour grandees, who previously campaigned for Britain to Leave the EU in the 1975 referendum, have penned an open letter explaining why they’ve changed their position.

Former Labour leader Neil Kinnock, Margaret Beckett, Hilary Benn, David Blunkett and Jack Straw have published a letter in support of the EU in the Sunday Mirror. The four who join Kinnock in signing this letter were ministers under previous Labour governments. Benn is currently shadow Foreign Secretary and is expected to play a big role in Labour’s EU strategy.

Although all five were once Eurosceptics, now they say “It’s clear Britain is stronger, safer and better off than we would or could be if pulled out of the EU.”

The five explain that their previous Euroscepticism was rooted in concerns that “membership would mean a one-way loss of sovereignty and investment.” “This has proved unfounded”, they write. They praise the EU for giving Britain economic partnership with 27 other countries, three million jobs and employment rights.

In a move that’s been interpreted as support for David Cameron’s attempt to renegotiate Britain’s relationship with the EU, they write: “The conclusion of the current renegotiation will hopefully strengthen this relationship as we make the progressive case for Britain in Europe.”

The Prime Minister is hoping to strike a deal at next week’s summit of EU leaders in Brussels. If this successful it would clear the way for Cameron to put the renegotiated terms of British membership to the public in a referendum in June.

The letter in full:

In the 1975 referendum we all campaigned against remaining in what is now the European Union.

Now, and for a long time past, it has been clear Britain is stronger, safer and better off than we would or could be if we pulled out.

Our concern then was that membership would mean a one-way loss of sovereignty and investment. This has proved unfounded.

We are part of an economic partnership with 27 other democracies, exercising full rights to determine agreed rules in the world’s largest single market.

That has brought three million jobs, it attracts large investment, promotes growth and provides for employment rights that protect British workers.

We also have control of our currency, borders, security, defence, foreign affairs and justice.

Britain’s voice on global matters, whether debt relief, peace-keeping or climate change, is amplified by being part of Europe. Intelligence sharing helps us fight terrorism and other crime.

The conclusion of the renegotiation will hopefully strengthen this relationship as we make the progressive case for Britain in Europe.

Leaving would be a huge risk to prosperity, security and the opportunities of future generations.

The EU is not perfect and improvement is always worth making, but the benefits far outweigh the costs.

– Neil Kinnock, Margaret Beckett, David Blunkett, Jack Straw and Hilary Benn