They have warned migrant crossings could create “unacceptable risks” for the city’s port and local services.

Portsmouth’s leaders have told the prime minister the city is “wholly unsuitable” for migrant small boat crossings.

In a letter to Andy Burnham, Portsmouth City Council chief executive Natalie Brahma-Pearl, council leader Councillor Steve Pitt and Portsmouth International Port director Mike Sellers raised concerns over the use of the city as a potential arrival point.

It follows the arrival of around 120 asylum seekers at Eastney on Sunday, September 6, after they were rescued from a small boat which had crossed the Channel from Normandy.

The landing was followed by a protest, with roads blocked and clashes between demonstrators and police.

The letter sets out “in the strongest possible terms” that Portsmouth is “wholly unsuitable for use as a disembarkation point for individuals arriving in the United Kingdom following migrant small boat crossings”.

It describes Portsmouth International Port as a “busy, commercially operating” facility which “constitutes designated critical national infrastructure and also serves as a contingency port for food imports in the event that the port of Dover is unavailable”.

The port is also described as a “critical lifeline” for the Channel Islands, with any disruption having “consequences well beyond the city, affecting island communities and businesses that rely on dependable and timely ferry and freight services”.

The letter warns that the “imposition” of small boat crossings would create “unacceptable risks” to the port’s commercial operation.

As a “significant cargo port”, it transfers “substantial volumes of fresh produce and other time-sensitive goods”, while cruise ships arrive twice a week on average, bringing “significant passenger numbers, transport movements and security requirements into an already constrained operational environment”.

“The combination of those activities with emergency or enforced disembarkation arrangements would be operationally unsafe, reputationally damaging and highly disruptive.

“Any direction requiring the port to be used for this purpose would materially damage that reputation due to the disruption caused and risk loss of business, for which Portsmouth City Council would expect full recompense from government.”

The letter also raises practical and safety concerns, stating that the port is not designed for the “reception, screening, safeguarding and onward transfer of vulnerable individuals arriving through irregular and unpredictable routes”.

It adds that the port is “configured for large commercial vessels, not lifeboats or small coastguard craft” and could be “unsafe” because of the “height of quays and berths”.

Providing welfare and medical care, as well as the safe movement of “unwell or vulnerable passengers”, would be “significantly compromised”, it says.

“These issues must be fully understood before any proposal to direct the port’s use for small boat arrivals could even be considered viable.”

The port is owned by the council, with its income reinvested directly into council services. The letter argues that any disruption to its income would mean the council “would expect full reimbursement” from the government.

The leaders also argue there is “no suitable location” elsewhere in the city, particularly on Portsea Island, which “only has three roads onto it which any obstruction or blockage, including access to the acute A&E hospital, would cause significant risk to not only Portsmouth, but Isle of Wight residents too”.

They called on the government to provide a “clear and unequivocal assurance” that the port, or any other council owned infrastructure, “will not be used as a disembarkation point for migrant small boat crossings”.

“Should government nevertheless seek to impose any form of direction or instruction on the port or Portsmouth City Council, we would make it clear that such action had been taken without local consent and that government would remain accountable to Portsmouth residents for the consequences.”

The letter also says the council has upheld its responsibility to accommodate asylum seekers, hosting more individuals than “anywhere else across the entire south east, whilst some councils continue to play no part whatsoever in assisting this national challenge”.

It concludes that it is “therefore inappropriate for the government to impose further pressure on Portsmouth, our infrastructure and local services, particularly given the council’s clear position that the Port and wider Portsmouth coastline are unsuitable for such purposes.”