The British Chambers of Commerce (BCC) said it expects output to increase by 0.9% this year, up from a previous prediction for growth of 0.6% after better-than-expected progress at the start of the year and a strong recovery in the services sector.
Earlier this year the BCC had cut its forecast for growth in 2013 from 1%.
It also lifted its forecast for gross domestic product (GDP) for 2014 - raised from 1.7% to 1.9% - and 2015 - up from 2.2% to 2.4%.
A BCC spokeswoman said it was the first time forecasts for three years had all been increased since before the financial crisis in 2008. But the body, which represents 104,000 business members with more than 5 million employees, warned that the pace of improvement was still poor and called for measures to boost capital investment.
BCC director general John Longworth said: "The upward revision in our growth forecasts is encouraging. Unfortunately, this does not change the fact that economic growth is still too weak and the pace of recovery will remain unduly slow for a while yet."
The BCC now expects to see 0.3% improvements in the second and third quarter, with 0.4% in the last three months of the year and 0.5% per quarter during 2014. It said while growth would remain modest until 2015, there would be a gradual medium-term improvement.
The powerhouse services sector, which represents the bulk of the economy, is likely to outperform other areas, it added.
The outlook boost comes in the wake of mixed views elsewhere. The Bank of England recently forecast growth being a little stronger, while the Organisation for Economic Cooperation and Development cut its prediction from 0.9% to 0.8% for the year.