Oil and gas exploration firm BG Group is facing growing opposition over plans to pay its new boss up to £14 million a year plus a £15 million "golden hello" ahead of a shareholder meeting to approve part of the package.

Helge Lund is to take over next year after 10 years in charge of Norwegian energy giant Statoil, with his appointment following the departure of Chris Finlayson as BG chief executive earlier this year, just 18 months into the job.

BG said Mr Lund was "ideally suited" for the role given his track record, skills and experience and his pay package was competitive within the oil and gas sector.

But investment advisory bodies have joined a chorus of discontent, with the Institute of Directors (IoD) saying the deal "brings the whole of British business into disrepute".

Mr Lund is due to receive a share award worth £12 million on joining but this is subject to approval by a special meeting of shareholders in Reading on December 15.

BG has warned that Mr Lund "is not obliged to join BG Group if the share award is not approved".

In addition, Mr Lund is in line for a one-off relocation allowance of £480,000 plus shares worth up to £3 million to compensate for unvested bonuses.

His base salary will be £1.5 million, with an additional £450,000 paid in lieu of pension plus an annual bonus worth up to £3 million and an annual long-term share grant worth up to £9 million.

IoD director general Simon Walker said: "The Institute of Directors is always reluctant to criticise an individual company.

"However, we do have a responsibility to criticise an action that brings the whole of British business in disrepute and threatens already-fragile attitudes to corporate Britain.

"It is excessive, inflammatory and contrary to the principles of good corporate governance.

"This pay deal would do serious damage to the reputation of British business six months ahead of a general election and at a time when the reputation of UK plc is still suffering.

"It is a red rag to enemies of the free market. We urge shareholders to call BG's bluff."

Proxy voting agency Institutional Shareholder Services (ISS), whose clients include key City fund managers, has called on investors to vote against.

It said: "The company states that Helge Lund might not join BG if this resolution is voted down by shareholders. But the alternative also has implications.

"Support for this proposal could encourage incoming executives (at BG and elsewhere) to negotiate rewards which are outside the scope of the formal remuneration policy and make shareholder approval a condition of their employment, on the assumption that shareholders are unlikely to vote down the proposal."

The Investment Management Association's voting advisory service has given the plan a "red-top" notice.

BG announced Mr Lund's appointment last month and two weeks ago said shareholders had "overwhelmingly welcomed the appointment", while, following feedback, it had tweaked his bonus package to strengthen its link to performance.

Previous boss Mr Finlayson quit in April citing personal reasons, in the wake of production targets being slashed due to continued problems in Egypt. Chairman Andrew Gould has taken the helm on an interim basis.

Last month BG reported a 29% fall in third-quarter earnings to £759 million.

The company was created in 1997 when British Gas demerged into two separately-listed companies, with Centrica having responsibility for the retail side of the business.