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
CCTV captures the moment two young children survive a car crash on their walk to school.
It will be a dry day and very warm with bright and sunny spells.
Armed officers will be on patrol at major infrastructure sites across Essex and the county will see more police patrols.