EasyJet is coming under increasing pressure over corporate governance issues ahead of its AGM next week.
Shareholder groups have highlighted problems with the make-up of the board and the company's bonus package for new chief executive Andrew Harrison.
PIRC, or Pensions Investment Research Consultants, has urged easyJet investors to vote against the low-cost airline's remuneration report on Wednesday.
And Research, Recommendations and Electronic Voting, the proxy voting arm of the National Association of Pension Funds, has advised shareholders to abstain.
The Association of British Insurers has yet to decide whether to put easyJet on "red top" alert. Proxy voting firm Manifest, meanwhile, has also flagged up issues for its clients, mostly local authority pension funds and some institutions.
RREV said issues have been thrown up by substantial changes to the board during the past 12 months, including a new CEO and CFO, as well as among non-executive directors.
It stopped short of recommending a vote against the resolution, as the controversial long-term incentive plan bonus programme put in place after Mr Harrison joined has not yet been used for the incomer.
But it added: "We consider votes consciously withheld (positive abstentions) to be a useful tool in communicating shareholders' reservations about a resolution, whilst not going as far as voting against."
PIRC's corporate governance policy manager David Somerlinck, meanwhile, said that Mr Harrison's package "has caused us problems".
He is worried that the scheme "sets a precedent, and if it happened a lot, it under-mines the effect of other incentive schemes".
He said this type of bonus can mean "shareholders end up paying a lot".
An easyJet spokesman said Mr Harrison was recruited before the LTIP was approved by shareholders, and that it should not therefore be labelled a "signing on bonus", as PIRC has described it.
As a replacement for the LTIP this year, Mr Harrison had been granted share options, he added.
RREV also highlighted an alleged governance flaw created by Jeff Carr's dual role.
Last March Mr Carr replaced Chris Walton as group finance director. He also serves as interim company secretary following the resignation of Deborah Abrehart at the end of 2005.
"Under the NAPF policy, we normally consider that the company secretary should not be an executive director, but we recognise that this is an interim measure pending the appointment of a new company secretary," REEV said.
Colin Chandler is also holding an interim dual role as a member of the audit committee and the chairman of the remuneration committee, against the provisions of the Combined Code on corporate governance.
Manifest also noted that the company had no adequate performance benchmark against which to judge its executive share plan. EasyJet claims there are not enough listed budget airlines to provide comparison.
It highlighted too the problem raised by Mr Carr's dual role, but noted that the "break with best practice" caused by the lack of a senior non-executive should be solved with the appointment of David Michels next month.
Research manager Alan Brett said that Manifest's clients, which account for over five per cent of the stock market, would have to decide which of these issues conflicted with their corporate governance expectations.
Any shareholder rebellion sparked by the concerns is likely to be muted, despite the reservations.