Britain will no longer be relevant to China if it goes through with Brexit, a senior French politician has said.

Emmanuel Macron, the former economy minister, has warned that outside of the European Union the UK will not have the protections afforded to a trading bloc and will therefore find it difficult to see off commercial competion from Beijing.

He said the UK alone would be incapable of stopping an influx of cheap imports and cited the recent crisis in the steel industry to demonstrate the difficulties Britain could face from the superpower.

“The UK is definitely not relevant to China. And the big mistake of countries is not to play the European game,” the Times reported Mr Macron as saying.

“During the past two years we were attacked by the Chinese, the Indians and the Russians and especially the Chinese on steel. An unfair attack. Nothing to do with globalisation and trade. They just had their own overcapacity.

“They didn’t want to deal with that and they inundated our markets, killing prices with their steel. Did we protect our industry and our workers? No. You saw that here in Port Talbot.”

Nigel Farage: Brexiters were "mildly irresponsible"

Mr Macron, who stepped down last month to contest the French presidency, also warned Brexit could kill the European Union in months.

“I think the UK has a choice: option one, you come back to the people and say Brexit was a mistake. It is impossible to be implemented. We will ask our people to think again about that through a general election or a new referendum. I respect that,” Mr Macron added.

Brexit reactions – in pictures Show all 10 1 /10 Brexit reactions – in pictures Brexit reactions – in pictures Supporters of the Stronger In campaign look at their phones after hearing results in the EU referendum at London's Royal Festival Hall AP Brexit reactions – in pictures Leave supporters cheer results at a Leave.eu party after polling stations closed in the Referendum on the European Union in London Reuters Brexit reactions – in pictures Mr Cameron announces his resignation to supporters Getty Brexit reactions – in pictures Donald Tusk proposes that the 27 remaining EU member states ‘start a wider reflection on the future of our union’ Getty Brexit reactions – in pictures Ukip leader Nigel Farage greets his supporters on College Green in Westminster, after Britain voted to leave the European Union PA Brexit reactions – in pictures Supporters of the Stronger In Campaign react as referendum results are announced today Getty Brexit reactions – in pictures Boris Johnson leaves his home today to discover a crowd of waiting journalists and police officers Getty Brexit reactions – in pictures Leave EU supporters celebrate as they watch the British EU Referendum results being televised at Millbank Tower in London Rex Brexit reactions – in pictures Supporters of the Stronger In Campaign react as results of the EU referendum are announced at the Royal Festival Hall Reuters Brexit reactions – in pictures Supporters of the Stronger In campaign react after hearing results in the EU referendum at London's Royal Festival Hall PA

“Second option: you want to implement the exit and try to find something new regarding free movement of labour.

“But if the rest of the EU agrees to allow Britain to limit free movement of people, in strategic and political terms there is a big incentive for all the other member states not to respect the rules of the club.

“And for sure in six months, one year or three years we have killed the European Union. I am not in favour of such a move.”