Mr Neill, a fervent supporter of Thatcherite union policies, also claimed that a high-profile speech by Labour leader Tony Blair in the Far East last year, advocating a stakeholder economy, was based on one of his own speeches.
Launching a typically scathing attack on Labour's employment policy, Mr Neill labelled the party's plans to force employers to recognise unions, which he said were part of a drive to implement the European Social Chapter, as "foolish" and "a step backward."
The policy states that employers should recognise unions in individual factories if a majority of staff votes for it.
Referring to recent moves by Unipart to invest more than pounds 90m in four joint ventures, Mr Neill warned: "We would not have made this investment if we'd had the Social Chapter. If we revert to that mindset it will have a profound impact on our forward investment plans."
Though Mr Neill's opposition to union recognition is well known, Unipart has a strong reputation for encouraging employee involvement, including its much publicised "University" for staff training. Unipart this year donated pounds 50,000 to Conservative Party coffers.
The most surprising claim was that Mr Blair had copied a speech by Mr Neill urging employers to adopt the vision of a stakeholder economy, a concept long advocated by the privately owned Unipart group. "That speech was based on one of my speeches. Peter Mandelson told me that," Mr Neill said.
A veteran of union disputes during a spell at British Leyland in the 1970s, he said: "I 'm not anti-union, I believe we've done things which mean there should be no need to have a union."
Asked whether Labour's policies had become more friendly to the business community, Mr Neill said:
"Blair has done a good job of leading his party but it's by no means clear whether he can run a complex economy. I suspect there are a lot of things we don't know about Labour's policies."