France has been urged to do more to stop illegal Channel crossings after scores of migrants were caught sailing to Britain last weekend.
There have also been calls for air surveillance of the English Channel to stop people from entering the UK illegally this summer.
Border Force officials detained 74 people, including small children, after eight boats were spotted off the Kent coast on Saturday.
Two vessels were also intercepted in France by the French authorities, the Home Office said.
Lucy Moreton, general secretary of the Immigration Service Union, said French authorities must take tougher action to prevent migrants from leaving their country.