Pub group JD Wetherspoon said it had received a boost from the Olympics but added it wouldn't be able to maintain sales at that level for the rest of the year.In the three months to 28th October - the company's first quarter - like-for-like sales increased by 7.1% and total sales increased by 11.1%.The firm saw its operating margin drop to 8.6%, around 0.4% lower than the last financial year.This was due to increased costs in areas such as tax, utilities, labour and bar and food supplies, combined with increased marketing costs, the firm said.The company opened two new pubs in the quarter and currently has eight pubs under development. It said it was on track to open around 25 pubs in the current financial year.As ever, Wetherspoons went on the offensive against the government over taxes and the treatment of pubs compared with supermarkets."The main challenges for the pub industry are the VAT disparity between supermarkets and pubs, combined with the continuing imposition of stealth taxes (which apply to pubs but not to supermarkets) such as the late-night levy and the increase in fruit/ slot machine taxes," it said."In spite of these challenges our sales, profit and cash flow remain resilient and the board continues to aim for a reasonable outcome in the current financial year."