"If Gordon Brown thinks he can march on and treat public sector workers in such a disgraceful way, think how he'd feel if he woke up one morning to headlines that said dozens of unions representing millions of public sector workers all say we're going on strike the same day," he said.
"I predict that if we have the courage to do that, Gordon Brown will change his mind," he added, to huge applause.
Brown's spokesman said there would be no retreat on pay, saying "difficult decisions" in recent years had helped keep inflation low, enabling the Bank of England to cut interest rates.
HEALTH WORKERS BACK DOWN
Ministers have negotiated multi-year pay deals for many public sector workers to keep inflation in check. Inflation is running at three percent, one percentage point above the Bank of England's target, reducing room for further rate cuts.
Workers argue the deals equal a pay cut and accuse the government of using inflation statistics that do not convey huge rises in food, housing and fuel costs.
Unison - the largest healthcare union - voted on Friday to accept a three-year pay offer worth 8.1 percent, bringing some relief to the government.
College lecturers in London, however, went on strike on Monday over pay and University and College Union General Secretary Sally Hunt said there would be more action across the country without a better pay offer.
The public sector threat comes on the back of protests by truck drivers and fishermen over high fuel prices.
National Health Service physiotherapist Sally Rudston, 35, said she was finding it difficult to make ends meet.
"It's really tough. Living costs, rent, petrol. Petrol is a big problem when we are working in the community visiting patients at home," she said on the sidelines of the rally.
