Natalie Elphicke, the Dover MP, said: “If migrants motoring across the Channel in small boats know they can stay in the UK even when they have no legal right to do so, then they will keep on coming, and in greater numbers. That’s what is happening.

“If other countries aren’t playing their part in returns, we must make sure the boats don’t get here in the first place.”

Tony Smith, a former director general of Border Force, said: “The problem is that we don’t have any safe third country agreements with the EU, and the current French administration is saying it won’t take any returns unless there is an agreement with the EU.

“The strategy has to be to reduce the intake and that can only be done by an agreement with France where migrants are instantly taken back to the point from where they came and their asylum applications dealt with there. At the moment, I can’t see the Macron administration agreeing to it.”

Even under the previous Dublin agreement with EU states for returns to safe countries, Home Office figures suggest that, in the 18 months to last October, fewer than 250 migrants who crossed the Channel were returned to mainland Europe – only 2.5 per cent of just under 10,000.

Ms Patel has said she intends to replace the Dublin regulation with bilateral arrangements and has already changed the law to make asylum claims in the UK inadmissible where people have travelled through, or have a connection to, safe countries.

Her new immigration plan, currently before Parliament, also proposes that illegal migrants will be denied asylum and face restricted residency rights in a bid to deter Channel crossings.

Chris Philp, the immigration minister, said: “All countries have a moral responsibility to tackle the issue of illegal migration. We expect our international partners to engage with us, building on our good current co-operation, and continue to highlight the importance of having effective returns agreements to stop people making perilous crossings.”