Marks and Spencer has reported sales growth ahead of expectations in the three months to 27 March.
UK like-for-like sales, which strip out new store openings, increased by 5.1%. Analysts had forecast a 1.7% rise.
The executive chairman of M&S also told the BBC he felt insulted by the prime minister's comments that company bosses had been deceived by the Conservatives.
Sir Stuart Rose is one of 68 business people to back Conservative plans to scrap a rise in National Insurance.
It is unfortunate that we have been dismissed. To insult the collective intelligence of 60-plus chief executives is not helpful
Sir Stuart Rose, M&S executive chairman
Labour has said it will increase National Insurance by 1% from April 2011, arguing that it is vital to maintaining public services. The Conservatives argue that it is a "jobs tax that will kill the recovery".
"It is unfortunate that we have been dismissed [by the prime minister]," Sir Stuart said.
"To insult the collective intelligence of 60-plus chief executives is not helpful. This is not a political point so much as a point about where tax should be levied."
Speaking later to the Today programme, Gordon Brown said: "I attach no blame to business. The Conservative party are misleading them."
Sir Stuart also denied that he had been offered a job and a peerage by Conservative leader David Cameron. And when asked if he would accept such an offer he replied, "Absolutely not."
The reported quarter includes the first day of the Christmas sale, 27 December
In its trading statement, Marks and Spencer said it had seen improvements across the board in the UK, with sales of general merchandise - which includes clothes - increasing 9.1% and food sales up 1.8%.
The retailer said sales of formalwear and knitwear were particularly strong.
Sales at its online shopping division M&S Direct were up 48%.
Its results were also boosted by the inclusion of the first day of the Christmas sale, which was not included in the corresponding quarter last year.
However, the retail giant said international sales fell 5.9% as a result of difficult trading conditions in the Irish Republic and Greece, while foreign exchange rates also had an adverse impact.
Last Updated at 22 May 2015, 11:30 ET*Chart shows local time
"These are strong quarterly results by any measure," Sir Stuart said. "We have weathered the immediate impact of the recession but remain cautious about the outlook for 2010-11 given the current challenging environment.
"We hope that after the election there will be greater clarity on economic policy and how this will impact our customers individually."
The company said it expected to make a pre-tax profit in the range of £620m to £630m for the year to 27 March.
The trading statement is the last to be presided over by Sir Stuart Rose. He will be replaced as chief executive by former Morrisons boss Marc Bolland in May, but will stay on in a part-time role as chairman.
Shares in M&S were down 1.4% to 373 pence in midday trading.
Keith Bowman, equity analyst at Hargreaves Lansdown Stockbrokers, said: "Despite headline reassurance, real belief in the group's long-term growth prospects has yet to be mustered - a task which now looks to fall to the new chief executive, Marc Bolland, in order to deliver."
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