Image copyright Cardiff Airport

Ministers have been accused of wasting tens of millions of pounds buying Cardiff Airport for around double an initial valuation of £20m-£30m.

Welsh Tory leader Andrew RT Davies accused Labour of a "stunning failure to safeguard taxpayers' money" in paying £52m for the airport in 2013.

The estimate by accountants KPMG is in a report by the Wales Audit Office.

The Welsh government said BBC reports based on those figures were "entirely selective and misleading".

Ministers bought Cardiff Airport from its Spanish owners Abertis for £52m, after another higher valuation from consultants Arup took into account other potential benefits of public ownership.

The deal followed years of concern about the airport's performance and long-term viability.

First Minister Carwyn Jones had defended the purchase as securing the airport's future as "a vital gateway to Wales", to be run at arm's length from government.

Image copyright Cardiff Airport

Publishing its report on Wednesday, the Wales Audit Office said it acknowledged time constraints but pointed to "some weaknesses" in the preparation of the business case for the deal.

On the purchase price, the watchdog noted that "commercial valuations can vary greatly depending on the assumptions applied".

It said the Welsh government had undertaken a "rigorous" process of due diligence, but it said the airport's need to borrow money was "greater than forecast at the time of acquisition", and that growth had been slower than predicted.

Auditor General Huw Vaughan Thomas said: "Turning the airport around is proving more challenging than the Welsh government expected at the time of the acquisition, despite some positive developments."

Media playback is unsupported on your device Media caption Andrew RT Davies says Welsh ministers showed a 'cavalier attitude' to public money

Welsh Tory leader Andrew RT Davies said it was "unforgiveable" for the Welsh government to have paid so much for the airport.

"This is yet another example of the Welsh Labour government's stunning failure to safeguard taxpayers' money, with tens of millions of pounds going to waste - despite clear, professional advice which should have told them that the price they were prepared to pay for the airport was over the odds," he said.

Welsh Liberal Democrats economy and transport spokesperson Eluned Parrott added: "This is another huge blow to the Labour government's already tattered economic reputation."

'Public value'

A Welsh government spokesman said reporting of the £20m-£30m valuation was "entirely selective and misleading".

"KPMG modelled a range of scenarios during the due diligence process," he said.

"The resulting valuations varied greatly depending on the cost of capital applied to the calculations.

"After taking further professional advice including a public asset valuation from Arup, the Welsh government concluded that a valuation of around £55m would be reasonable from a commercial perspective.

"The public asset valuation of £472m [taking into account the airport's wider value to the Welsh economy] also justified the price paid on public value for money grounds."

He added: "We were right to rescue Cardiff Airport from a downward spiral in private ownership and the report by the Auditor General for Wales confirms we took appropriate due diligence before purchasing the airport and that the governance arrangements since the acquisition have had a positive impact."

Analysis by Brian Meechan, BBC Wales business correspondent

The public spending watchdog, the Wales Audit Office, says ministers undertook appropriate due diligence before buying the airport.

This means they'd undertaken all the sensible measures expected of people when they take over a company.

Valuations, though, are not straightforward and depend on the assumptions of the buyers.

The issue is that something is worth what someone is willing to pay for it.

The Welsh government made it clear that it thought the airport was an embarrassment to Wales and it wanted to take it over.

It faced a seller who was happy to keep hold of the site. That in itself would push the price up.

It's a widely held view in the business community that the Welsh government did overpay for the airport.

However, since it has taken over at Cardiff, it's certainly seen passenger numbers increase and facilities improve.