Scotland's largest teaching union said it would consider the potential for strike action at a special meeting this weekend. The threat came as doctors' leaders and unions representing health workers, civil servants and other public-service staff also warned they would fight the plans.
It followed confirmation from the Tory-LibDem Coalition yesterday that millions of public-sector staff would have to work longer for a smaller pension.
In response, the Educational Institute of Scotland (EIS) said the prospect of a walkout was "very real".
Ministers insist the moves are necessary to ensure public-sector pensions are affordable in the face of a rapidly aging population.
Business leaders, including the CBI, have backed the plans and told ministers to "stick to their guns" against union opposition.
However, Larry Flanagan, general secretary of the EIS, said teachers would not "meekly" accept the plans to link their pensions to the state pension age. The changes would see many teachers working until their late 60s and possibly even later, he warned.
Mr Flanagan added that teaching was too physically demanding and it was "inconceivable teachers should remain in charge of classes until they are almost 70 years of age".
Teachers had accepted some changes to their pensions would be inevitable, he said, but he warned they could not accept being forced to continue working into their late sixties.
"It's an issue teachers are prepared to fight on, and the prospect of further industrial action in defence of our pension rights is very real," he added.
The threat will put more pressure on the Scottish Government to offer teachers a "Scottish solution".
In March the EIS agreed to suspend a planned one-day strike to enter talks on the issue with the Scottish Government and councils.
The EIS says Scottish ministers have the power to offer flexibility around pensions as long as there is no increased cost to the Treasury. Options could include Scottish teachers agreeing to pay more into their pensions in return for being able to retire earlier.
Changes outlined yesterday by the UK Government will mean millions of public-sector workers will have to wait until 68 to get their pension, in line with huge numbers in the private sector.
However, that age could rise as Coalition ministers have also pledged to consider increasing the state pension age as the population ages.
Many teachers in Scotland can retire at 60, although some new entrants to the profession must work until 65.
Teachers in England have already announced plans for a campaign of industrial action short of a strike over pensions from later this month.
Doctors' leaders also protested against plans to make NHS staff work longer and pay more into their pensions.
Dr Mark Porter, chairman of the Council of the British Medical Association – which held a one-day strike over pensions earlier this year – said: "Work in the NHS is physically, mentally and emotionally demanding, and some staff will not feel able to work effectively beyond the age of 65."
Union leaders have also appealed to disaffected LibDem MPs to help them fight the changes from within the Coalition. Unite, the public-sector union, also accused ministers of giving the "untrue" impression that workforces had agreed to the plans.
Last November 1.5 million public-sector workers, including 300,000 in Scotland, staged a one-day walkout in protest at plans to change their pensions.
The UK Government's plans include moving millions of public-sector workers on to "career average" instead of final salary pension schemes. Although most will also see their pensions linked to the state pension age, there will be exemptions for the Armed Forces, police officers and firefighters.
Workers will also be protected from the changes if they are less than 10 years from retirement.
A Scottish Government spokesman said: "Public-sector pensions must be affordable, sustainable and fair, and negotiated in partnership with unions and employer representatives.
"The UK Government's Bill places significant constraints on the Scottish Government's ability to ensure a fair agreement which reflects Scottish circumstances. We are working closely with employers and trade unions to secure a Scottish solution.
"Scottish public-sector workers deserve certainty about their future pension terms.
Those who argue a need to rein in public-sector pensions point to the large number of final salary schemes in the private sector which have been closed to new members or contributions in recent years.
Of the 23 million people who work for private businesses in the UK, only 3.2 million pay into a workplace pension that also includes a contribution from their employer. Public-sector staff who pay into a pension enjoy generous employer contributions, funded by the taxpayer.
A commission set up by the National Association of Pension Funds (NAPF) recently reported millions of private-sector workers faced a "bleak old age" because they fell through the cracks of pension provision.
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