As many as 150,000 additional people will be caught out by the extension of higher-rate tax relief restrictions.
In his pre-budget report, Alistair Darling announced higher-rate tax relief restrictions - originally announced in April's budget - will now include employer contributions and affect those with relevant income of £130,000 and over rather than the previously announced figure of £150,000 and over.
This will effectively mean anyone with income of £130,000 or more will not receive higher-rate tax relief on their contributions.
A statement by The Treasury confirmed: "From April 2011 tax relief on pension contributions will be restricted for individuals with gross incomes of £150,000 and over, where gross income incorporates all pension contributions, including the value of any benefit funded by, or eventually funded by, an individual's employer.
"Tax relief will gradually be tapered away so that above £180,000 it is worth 20%, the same rate received by a basic-rate income taxpayer. To provide more certainty for individuals around whether they are affected, and to reduce administrative burdens for schemes, this will be subject to an income floor at £130,000 of pre-tax income (excluding the value of any employer pension contributions)."
Standard Life senior pensions policy manager Andrew Tully said the extension of the restrictions was a "disappointing" - and could mean as many as 150,000 additional people would be affected.
He said: "This is a very disappointing move, further breaking the long-standing principle that an individual receives tax relief on their pension contributions at their highest marginal rate.
"Continuous changes to pension tax rules do nothing to encourage saving, and we urge the Government not to proceed with this move. We need clear, simple rules for the long-term to encourage more people to save and help address chronic under-saving in the UK."
Hewitt Associates principal consultant Martin Bird thought around 70,000 additional individuals would be caught by the new salary definition moving from £150k to £130k.
He said: "This measure means that more people will be caught, while there will also be more uncertainty as we won't know how the rules will interact with other areas of pensions taxation, and there will be yet more complication in the system.
"The government is introducing more obligations on employers, scheme administrators and trustees, all of which will add to the costs of running schemes. Once again, pensions "simplification" is right out of the window."
Towers Perrin head of pensions Mark Duke agreed: "To hit the Government's tax gathering target, it has been decided to increase the affected group by around 30%. This has been achieved by counting company pension contributions as income when testing whether someone has breached the £150,000 per annum threshold."
He added: "The pensions tax regime is set to become an administrative quagmire. Employees with higher incomes and pension plans will be confronted with a plethora of new rules as they try to work out whether and what extra tax is due.
"The pension changes are part of an unshakeable policy goal to collect more tax from the better off. Lobbying efforts must now focus on damage limitation by trying to make the new rules workable."
The government has also launched a formal consultation on the implementation of the restrictions.
The consultation will run for 12 weeks until March 3, 2010 and will allow core legislation to be in place ahead of implementation in 2011, providing certainty for those affected.
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Some 2,000 consumers affected