Kate Middleton's parents' attendance at a Balmoral event has sparked rumours of an imminent royal engagement.

The brunette beauty - who has been dating Prince William for seven years - took her parents Michael and Carole Middleton along to a private shooting party at Queen Elizabeth's Balmoral Estate in Scotland, which according to aides, suggests they have been accepted into the royal fold.

One told the Daily Mail newspaper: "William and Kate do go up to Balmoral quite a bit, but inviting her parents is a big deal. This is virtually confirmation they're his in-laws-to-be.

"Carole must be absolutely ecstatic. She's finally made it right inside the royal circle."

The Middleton parents were part of a group who had been specially invited to the residence by Prince William for his annual country pursuits house party.

It is widely rumoured Kate and William are planning to get engaged in early 2011, with a lavish ceremony taking place the following summer.