Sarah Jessica Parker's marriage to Matthew Broderick has come under the spotlight following allegations that the actor cheated on his wife of 11 years.

According to a US report, Broderick struck up a relationship with a 25-year-old youth counselor earlier this year.

A friend of the woman in question tells Star magazine that the pair began texting each other and before long were enjoying passionate encounters at a townhouse owned by one of the actor's friends.

Parker has previously spoken candidly about her rocky marriage.

In an April interview she said, "I'm really lucky that he is the father of my son, but that doesn't mean that we always agree on everything. We've had some rather treacherous train rides.

"I'm happy to be with him regardless but I'm sure there are many times he wishes he wasn't with me."

The couple - who has a five-year-old son, James - are yet to respond to the story.