Ireland’s prime minister has insisted the UK must respect an existing arrangement between the two countries to take back asylum seekers.

Simon Harris told Sky News the UK must honour a deal that has been in place since 2020 as a row escalates over the Irish government’s new plans to return to the UK asylum seekers who cross the border into the Republic from Northern Ireland.

Irish justice minister Helen McEntee told a parliamentary committee last week that more than 80% of recent arrivals in Ireland came via the land border with Northern Ireland.

The UK government has said it will not take back asylum seekers who cross the border into Ireland “until the EU accepts that we can send them back to France”.

The number of migrants crossing the English Channel from the continent in small boats during the first four months of the year reached its highest ever level at the weekend.

On Tuesday morning, Irish PM Mr Harris told Sky News: “There is already an agreement in place between Ireland and Britain since 2020.

“What we’re doing is giving legal clarity in relation to that agreement which will allow us to designate the UK as a safe country again.

“It’s also very important for people in Britain to understand that this is a two-way agreement.

“This is to ensure that refugees can be sent in both directions if their application is inadmissible.

“We also have a legitimate expectation that agreements between our two countries are honoured.”

Rishi Sunak’s spokesman said there are “operational arrangements” between the UK and Ireland but insisted there is “not a legal obligation to accept the return of asylum seekers and under those operational arrangements no asylum seekers have been returned to the UK”.

“It’s up to the UK government who we do and do not accept into the country,” he added.

The row between the two countries comes as the UK government’s plan to send asylum seekers to Rwanda came into law last week.

Ireland’s deputy prime minister and foreign secretary Micheal Martin said the threat of deportation to Rwanda was causing “fearful” migrants to head for Ireland instead of the UK.

Mr Harris said on Sunday Ireland would “not provide a loophole for anybody else’s migration challenges”.

He added on Tuesday that the largest percentage of people coming to Ireland illegally recently has been from Nigeria so last week they brought in fast-track applications for people from Nigeria.

“We have every right to have our own migration policy,” he told Sky News.

“People have every expectation that it would be enforced, that it would be firm, that it would be rules-based.

“And I think we also all have a legitimate expectation that agreements between two countries are honoured.”

A major operation by the Home Office to detain migrants across the UK in preparation for their deportation to Rwanda has begun “weeks earlier than expected”.

But it has been reported that more than half of the asylum seekers allocated for removal to Rwanda cannot be found, according to the government’s own impact assessment.

Ministers from the UK and Ireland met in London on Monday as part of a planned conference, involving Mr Martin and the Northern Ireland secretary, Chris Heaton-Harris.