The longest-serving MEP in the UK has said the country will not rejoin the EU in his lifetime – and may never return to the bloc.

The former Labour MEP, David Martin, who represented Scotland in the European Parliament from 1984 to 2019 said that even a pro-European government would find it almost impossible to rejoin the EU and that the UK’s favourable membership terms would not be offered in new accession talks.

He told Scotland on Sunday: "There is no going back, and I think we are now, for at least the rest of my life and possibly forever, a third country as far as the European Union is concerned.

“I don’t think anybody could kid themselves that there’s a quick way back in. Once you’re out, you’re out, and all the benefits, if they were benefits – of not being part of the euro, having a budget rebate, not being part of Schengen – none of these things will we get again if we were to renegotiate.

“So I think even if there’s a change of government in five years’ time with a more pro-European view, membership is not going to be negotiated, so that’s gone.”

And he issues a warning about the negotiation of a trade deal and the timescale that Boris Johnson and his government believes is feasible.

He added: “Singapore took nine years from start to finish to negotiate a trade deal. That was a fairly straightforward trade deal. It’s naive in the extreme to think that the UK can do it in nine months.

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“My fear is we’re heading for a series of many deals to, as it were, literally keep the planes flying between Britain and Europe, to keep goods moving.

“I think the business side, the trade side is looking extremely, extremely negative… if there are a series of small trade deals, actually the momentum in terms of getting a big deal will disappear and it could be a long time, if ever, before you get a deal.

“No deal in a pure sense was never a possibility in relation to Brexit. No deal in terms of trade is a possibility because some things have to happen if there’s not going to be mutually assured destruction.

“But once these essentials happen, as I say, the motivation to carry on negotiating could diminish.”

Martin also issues a warning to those areas that had benefited from EU investment and services such as universities, saying: “It was the European Union that invested millions in the former coalfield areas, and regenerated those coalfield areas.

“If you look around places that are very close to Edinburgh, like Newtongrange and Bonnyrigg and parts of Midlothian, villages could have literally died if it hadn’t been for the investment that came from the European Union.”

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Touching on Scottish independence and the prospect of a future referendum, Martin told Scotland on Sunday the UK “needs to change the way in which it respects the views of the nations” if it is to survive.

“My view has been for a while, leaving the EU is a fundamental change of circumstances and the once-in-a-generation argument does not apply in that situation, because we are in a different ballgame,” he said.

“I’m still in the position where, because there are so many uncertainties, I have no idea what I would do in such a referendum. But the right to hold it and to have that national debate is now almost unquestionable.”