The economy was actually growing when the Coalition took over and continued to do so for a couple of months until Osborne's first budget sent it plummeting again. It is mainly this plummeting we are beginning to recover from (after nearly four years).
If you look at the graph accompanying the report below, you will see that apart from the Credit Crunch Crash of 2008 (nothing to do with the government in power - and a dire situation from which Labour recovered much better than so many of our contemporaries - Greece, Spain, Iceland, Ireland spring to mind) that Labour's record on economic growth was marginally better than the Coalition's.
Osborne has "generated" this growth by first suppressing it for four years to give a fifth year "glow" - a strategy of bust then boom much employed by Tory Governments to create a (falsely-based) feelgood factor prior to a General Election. The short-memoried electorate often fall for it.
http://www.bbc.co.uk/news/business-27203433