Jon Hamm has defended his hit TV show Mad Men, insisting it is not sexist.

The actor plays womanising Don Draper in the award-winning programme. Mad Men is set during the 60s and centres on an advertising agency in New York. Many of the female characters in the show are secretaries or housewives, but Jon insists Mad Men offers a realistic representation of that period in time.

"On the surface it seems as though the female characters are secondary or oppressed in some way," he told British newspaper The Sun. "But in reality we are seeing the beginning of how they are breaking through the ceiling."

Series five is finally due to hit screens next month. The latest episodes were held up by contract negotiations and Jon admits he was eager to get the cameras rolling.

"It was frustrating but understandable. There were a lot of factors at work that were totally out of our control," he explained. "Sometimes you are at the mercy of other people but it was completely worth the wait."

Jon has refused to give away any of the plot details from the new series. However, he did reveal it would "continue the story".

"We have established this world our characters live in," he added. "It's a very colourful and exciting world and we are going to keep everyone in there and keep them bumping into each other and see what happens."