NORTH Sea cost increases and exploration reverses have taken a heavy toll on Cairn Energy, which has posted a $1.1 billion (£660 million) loss and shelved share buy backs amid a tax dispute in India sending its shares plunging.

The Edinburgh-based company saw losses increase five fold in 2013 as it faced big challenges in the UK and overseas.

Cairn provided $251m against the value of the planned Catcher development 110 miles south east of Aberdeen after cutting its estimates of the size of the find while increasing cost projections.

The company incurred $81m costs for unsuccessful wells in the North Sea.

Cairn also booked $107m charges in respect of its Moroccan exploration programme, in which it has suffered two setbacks recently.

The reverses may raise questions about Cairn's strategy, which combines exploring so-called frontier areas like offshore Morocco with less risky activity in North Sea.

Renowned for making big finds in India in the first decade of the century, Cairn has since spent $1bn off Greenland without making a commercial find.

The company said yesterday it has halted a $300m buy back programme launched in October, which is a third complete, pending resolution of a tax dispute in India.

Authorities there have requested information about the reorganisation of Cairn's former subsidiary in India in 2006, ahead of its flotation on the country's stock market.

"We're confident that we've done the right thing; we've been good corporate citizens in India and good tax-payers," said Cairn's chief executive Simon Thomson, who dismissed a report it has received a $1bn tax demand.

However, the authorities have stopped Cairn from selling the company's remaining holding in its Indian business. This is on Cairn's books at $1bn. Cairn sold a controlling stake in the business to Vedanta for $5.5bn in 2011.

Cairn provided $268m against the value of its holding in 2013.

The update appeared to rattle investors yesterday when shares in Cairn closed down 14%, 28.3p, at 168.2p. That reduced Cairn's stock market worth by around £160m, to £975m.

Shares traded at around 300p in April last year.

But Mr Thomson defended the progress the company has made since he succeeded its founder Sir Bill Gammell as chief executive in summer 2011.

"We set out to rebuild a portfolio, we've done that. We set out to deliver a high impact programme, we've done that, we're working our way through it. We wanted to establish a core (North Sea) development asset base for future production, we've done that and we've also returned additional cash to shareholders."

Cairn expects to drill seven wells in the coming year, including two off Senegal and one off Ireland. It will not decide until next year about drilling any more wells off Greenland.

On Monday Cairn said its latest well off Morocco was dry. The company moved into Morocco through the £414m acquisition of Nautical in 2012.

This also gave Cairn stakes in big North Sea discoveries like Catcher. Cairn increased its exposure to the North sea through the £280m takeover of Agora Oil & Gas soon after.

Asked if Cairn had overpaid for Nautical, Mr Thomson said: "Our view is that the value of the group of assets that we acquired under those transactions has increased."

Cairn expects the Kraken field off Shetland to come onstream by mid 2017. Its share of production is expected to be 12,500 barrels daily.

Mr Thomson said: "Unfortunately you don't write up assets for accounting purposes and the value of Kraken has increased."

He said Cairn could increase its exposure to the UK and Norwegian North Sea.

The company said it will participate in the 28th UK Licencing Round

Mr Thomson said George Osborne should maintain fiscal stability for the North Sea in the 2014 Budget today.

Asked if he had any concerns about Scotland voting for independence in September, Mr Thomson said: "Whether it's part of the UK or independent the key answer for us is continued fiscal stability."

Regarding Greenland, Cairn said it remains encouraged by the opportunity in the Pitu exploration block and is targeting a drilling decision in 2015.

Cairn lost $1.1bn on continuing operations before tax in 2013 and $194m in the preceding year. It had $1.25bn cash at 31 December.

Sir Bill will retire from the board after the meeting on May 15 and will be succeeded by Ian Tyler.