There had been widespread speculation that Mid Bedfordshire MP had been contemplating a move to UKIP.
However, it is understood the Ukip issue did not come up at her meeting with Sir George this afternoon, which was described as "convivial".
Ms Dorries said: "I am delighted. It is long overdue."
More top news
A crowd-funding campaign to buy The Duke of Marlborough pub in Somersham near Ipswich has reached £200,000.
A very windy and wet night in store this evening with gales- some severe on Sunday.
A group of kind-hearted mums from Northamptonshire have launched a campaign to try and help older people living alone in their community.