UK oil firm Cairn Energy has gained the right to seize Indian state assets in France worth more than €20m (£17m) as part of a long-running tax row.

A French tribunal ordered a freeze on about 20 properties in central Paris as Cairn increases pressure on the Indian government over disputed tax claims.

Cairn said it wanted an "amicable settlement" in the $1.2bn (£870m) row.

Sources said the Indian government would seek "legal remedies" when it received notice from the French court.

Edinburgh-based oil and gas exploration firm Cairn Energy is in dispute with the Indian government over a 2014 retrospective tax bill, when the country's tax office seized a 10% stake in Indian operations that Cairn was trying to sell.

Cairn took the issue to an international tribunal, which awarded the company $1.7bn in costs and damages in December 2020. The Indian government has appealed against this.

However, the energy firm has been identifying assets that it would seize in the absence of a settlement, including some belonging to Air India.

The award by the French court is "a necessary preparatory step to taking ownership of the properties and ensures that the proceeds of any sales would be due to Cairn", the company said.

David Nisbet, director for group corporate affairs at Cairn Energy, told the BBC's Today programme: "It is a long-running story unfortunately, and one we wished hadn't actually taken place.

"Clearly what we want to do is find an agreed amicable settlement with the government of India," he said. "But this is all just part of a process of saying: 'Look India, we need to earnestly engage', but we also have a fiduciary duty to protect the rights of our shareholders."

He said that more than six months after the ruling by the international tribunal, despite discussions in Delhi on two occasions, India has not said it will honour it.

"We have to protect the rights of our shareholders," he said. "And our international shareholders, who have waited patiently for seven and half years, would expect us to do so."

The Indian government has said that it does not recognise international tribunal awards, and that tax is a sovereign matter.

Mr Nisbet said that Cairn Energy had never questioned the right of any government to levy taxes.

However, he said that the Indian government had fully participated in the five-year international arbitration process, and that it was a signatory to an investment treaty between the UK and India.

Cairn expects the Indian government to honour the both the ruling and the treaty.

The Indian government declined to comment, but sources said it had "not received any notice, order or communication, in this regard, from any French court".

"We are trying to ascertain the facts, and whenever such an order is received, the government of India will take appropriate legal remedies in consultation with its counsels," the sources said.

The sources added that the government filed an application on 22 March to set aside the award by the international tribunal in The Hague Court of Appeal, adding that the government of India "will vigorously defend its case".

Analysis box by Dominic O'Connell, business correspondent

A thorn in the side of India's government

Trying to seize planes or property owned, or linked, to a foreign government in pursuit of an unpaid debt might sound an extreme tactic. But there is plenty of precedent for what Cairn is doing.

Lenders or investors trying to secure money they believe they are owed have often asked the courts for help. The normal route is to target assets that are in jurisdictions outside the control of the government being pursued.

Aircraft, which are valuable, mobile, and relatively easy to sell on, are a frequent target.

In 2012 Elliott, the investment firm currently trying to shake up the UK pharmaceuticals company GlaxoSmithKline, went one step further, persuading officials in Ghana to arrest an Argentine naval training vessel.

Elliott was trying to enforce payment on sovereign bonds issued by the Argentine government.

These are, of course, tactics in a bigger battle. Cairn does not have any particular interest in trying to seize and resell Air India aircraft or the clutch of properties it has seized in France.

What it wants is to be a thorn in the Indian government's side.

The legal actions will, Cairn hopes, push India into a negotiated settlement - to avoid further court battles and another wave of bad publicity.