Two separate groups were picked up on Friday, totalling 12 people.
One group of eight migrants on board a dinghy were spotted by the Pride of Kent passenger ferry, which alerted a coastguard vessel.
After being rescued they were taken back to Dover, where some of the group were being treated for hypothermia, according to Sky sources.
Earlier at around 3am a group of four migrants – one Syrian and three Iranians – was also rescued.
The operations come after dozens of people have been rescued in recent days, with the numbers described as “deeply concerning” by the government.
Labour’s shadow home secretary Diane Abbott called for better cooperation with the French authorities.
Organised crime gangs are blamed for carrying out the crossings.
Officials intercepted 23 Iranians in the Channel on Thursday, including three children, and 43 were picked up over Christmas Day and Boxing Day.
A former senior Home Office official has said smugglers are emboldened by the fact that UK lifeboats are rescuing travellers out at sea – with the rescuers then taking them on to dry land where the can claim asylum.
David Wood, who used to lead immigration enforcement, warned there could be a tragedy unless the government changed its policy to stop migrants coming rather than rescuing them and landing them on British shores.
Mr Wood said: “Britain’s border force, coastguards and lifeboats are being used as a taxi service for migrants. As far as organised crime is concerned, it’s de-risked their business.
“They know they don’t have to get right across the Channel and land, they can get half way across and the migrants will be taken the rest of the way.
“We have to stop this or it will grow and grow. The answer is to return them to France as soon as they are picked up. Given that the immigrants travelled from France, it would not be unlawful if the French agreed.”
Warning of the risk that the situation could turn to tragedy, Mr Wood added: “There will be a hue and cry when a boat full of 12 migrants sinks and they die.”
Dover MP Charlie Elphicke has called for the Home Office to take the problem more seriously and step up resources along the Kent coast.