The 35-year-old musician and the charity campaigner never saw eye-to-eye throughout Heather's marriage to Paul - which ended acrimoniously in 2006 before they eventually divorced in 2008 - and he partly blames her for his estrangement from his dad.
James was already at a low point in his life after his mother Linda McCartney died from breast cancer in April 1998, at the age of just 56, and when Paul met Heather in 1999 it caused a rift between father and son.
Speaking to the Daily Mirror newspaper, James said: ''It was a difficult time. Dad was married to Heather and we didn't get on. I was so into Kurt Cobain and this mentality so I didn't really like her. It was very difficult, I had my own issues ... The estrangement was partly because of Heather. It was difficult because of mum's death and then moving on, having a new mother. We drifted quite far apart, it was a difficult period. I had to strike out on my own and I needed a bit of time to grieve my mum's death ... I started getting more into Class A drugs, ketamine. I wasn't doing heroin. At the time I severed that tie with the rest of the family a little bit which I wish I hadn't done now.''
James eventually sought treatment for his substance abuse problems and got clean and started to repair his relationship his Beatles star father.
The singer/songwriter insists he and Paul, 70, are now closer than ever and he has nothing but good things to say about his dad's new wife Nancy Shevell - who he tied the knot with in 2011.
James - who has three older sisters, Heather, Mary and Stella - said: ''They (my sisters) are happy that the ties are back now and with dad, we are great mates now. I definitely want to embrace the relationships I have with the people I love. Especially someone like dad, who is my best friend ... His new wife Nancy is great. Nancy's my new mother. I feel that. Definitely. She's very genuine. She makes dad very, very happy. We all adore her.''
James - who has just released his debut album 'Me' - also has a younger sister, nine-year-old Beatrice, Paul's child with Heather.