The boss of Newcastle International Airport last night insisted an investigation will clear his name, just hours after his resignation was announced.

Chief executive John Parkin was removed from his day-to-day duties in March, when airport bosses announced an inquiry had been launched into "certain personal contractual issues".

Yesterday - nearly two months after his suspension - it was announced that the 52-year-old had resigned. He handed in his notice last Friday with immediate effect.

But speaking for the first time since his suspension, he told The Journal he would be vindicated during the probe into "contractual issues".

In a statement, he said: "Due to the on-going inquiry, it would be inappropriate for me to comment in full at this time for legal reasons.

"However, I am confident that I have fulfilled all of my contractual obligations to Newcastle International Airport and that the inquiry will confirm this in due course.

"I would only add that I am very proud of my record as chief executive of Newcastle International Airport since 2002 and of my achievements while in that post."

Speculation has been rife over the circumstances of Mr Parkin's suspension, but over the last two months airport bosses have refused to release any further details.

In the wake of the resignation, Newcastle Central MP Jim Cousins expressed his surprise, particularly in the light of Mr Parkin's success at the airport, but demanded more transparency over the inquiry.

Referring to the investigation as a matter of "public interest", he said: "I think some account needs to be given. The only account that has been given so far refers to contractual issues, which is very vague."

He added it could be "damaging" both for him and the airport for it go "without clarification".

Last night airport bosses again insisted legal reasons prevented them from releasing any further details.

A statement said: "Following a statement issued on March 23, 2007, concerning the suspension of John Parkin, chief executive, and an associated ongoing investigation into certain personal contractual issues, Newcastle International Airport Limited confirms that Mr Parkin has resigned from the company with effect from Friday, May 11, 2007.

"Since March 23, significant progress has been made in connection with the investigation into the personal contractual issues and Mr Parkin's resignation does not affect or impact on the ongoing inquiry."

Heading of planning and corporate affairs Graeme Mason yesterday refused to be drawn on a time-scale over the investigation, but insisted it was business as usual at the airport. The airport company is jointly owned by seven North-East councils - which between them have 51% of the shares - and Copenhagen Airports.

South Tyneside Council acts as the "lead authority" on the local authority holding company, but yesterday a spokesman declined to comment on the resignation.

Other councils also refused to comment on the issue.

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Take-off came with the budget airlines

Former chief executive John Parkin was credited with transforming Newcastle into one of the fastest growing airports outside London.

The 52-year-old, who is also a board member of the Newcastle Gateshead Initiative Marketing Agency, came to Newcastle in June 2002 from Bristol International Airport, where he had spent five years as managing director.

Before that, he had worked with Thomas Cook Group, and P&O and Princess Cruises Europe.

During his time at the airport, he oversaw the arrival of budget air travel, with airlines including easyJet setting up a regional base in 2003.

He was praised for making a commercial success of the airport and this was borne out earlier this year when he announced the first scheduled long-haul flights from the city with the arrival of Emirates.

He also oversaw a one-off £80m dividend to be shared among seven local council stakeholders and co-owners Copenhagen Airports. The deal followed a refinancing package.

After Mr Parkin's suspension, David Laws - previously the only other executive director - took over as chief executive.

Mr Laws, who has worked at the airport for 28 years, previously held the role of aviation and commercial director.

At the time of Mr Parkin's suspension, it was also revealed a third executive director was being appointed. Simon Fisher took up the position of finance director and company secretary.