The RSA think tank has estimated that the total number of self-employed in the UK will rise from its current total of 4.4 million to 5m by 2018.
At the same time, the number of public sector workers is projected to fall from 5.7m to 4.9m as government austerity measures continue shrink the state sector.
With the numbers of "micro-businesses" - defined as firms with nine or fewer employees - also on the rise, the RSA said politicians will increasingly have to take account of the small business vote. Since 2008, the RSA said that the number of microbusinesses had risen by 620,000 - a 13% increase - and now accounted for 95% of all private sector businesses and 32% of private sector employment.
However, a Populus poll of 1006 microbusinesses, commissioned by the RSA, found 65% thought the Government was not providing sufficient support while 61% thought the welfare system was unfair to the self-employed and small business owners.
There was strong support for a "significant" cap on immigration - 63% - but views were divided on Britain's membership of the EU with 37% saying they would vote to leave in a referendum as against 40% who would vote to stay.
The Tories were judged to have the best policies for small business by 46%, with 10% for Labour, 7% for Ukip and 5% for the LibDems.
RSA senior researcher Benedict Dellot said: "Microbusinesses are the new political force to be reckoned with, but the Government has yet to win their favour.