Large numbers of small boats will attempt to cross from France to Britain’s South Coast after a mega-dinghy reached Portsmouth at the weekend, it has been warned.

French officials predicted ‘far more’ migrant dinghies will make the long distance sea voyage from Normandy in the coming weeks.

British experts urged the Home Office to begin preparing for a new escalation of the Channel crisis after an inflatable with 140 people aboard arrived in Portsmouth on Sunday, prompting ugly scenes as protesters clashed with police.

The dinghy had travelled about 70 miles from the Normandy coast – the first migrant boat to make such a lengthy crossing.

Its route was hundreds of miles from the usual transit point between Calais and Dover.

A senior French interior ministry source told the Daily Mail: ‘The geographical focus of the people smugglers is definitely changing.

‘They are finding it much harder to get boats launched in the Pas-de-Calais and so are moving west, across to Normandy.

‘We expect far more of the mega-dinghies to appear here in the coming weeks and months.

‘The success on Sunday proved the voyage can be done.’

The Home Office confirmed 625 migrants reached Britain on Sunday, the highest daily total since July 29.

A further as-yet-unconfirmed number, thought to be about 130, arrived in the early hours of Monday.

Occupants of the Portsmouth dinghy, including 20 women and eight ‘very young children’, refused rescue after their outboard motor broke down, according to French officials.

The 46ft mega-dinghy left an isolated beach near Jobourg, Normandy, in the ‘very early hours’ of Sunday morning, a senior search-and-rescue official said.

‘Jobourg is not patrolled by police, because nobody would expect a boat to leave from such an isolated, rocky spot,’ the source said.

‘Within an hour or so the boat was in serious difficulty, and passengers on board made Mayday calls on their mobile phones.’

Read More: More migrant small boats will follow long distance route to Britain’s South Coast