The research, from the Independent Television Commission (ITC), calculated that BBC 3 would attract a far bigger audience than first thought, costing commercial rivals up to £25m in lost revenue. The BBC had put the figure closer to £4m.
Jowell has asked the two bodies to come together to try to reconcile the figure and produce a report which is expected to form the basis of her decision on the channel - now expected in early April.
Jowell, speaking at the Westminster Media Forum in London on Tuesday (12 March), said poor economic conditions had made her decision on the new youth channel even more difficult.
?I am concerned about saying yes to a bid that is too competitive, especially as many commercial companies are currently feeling the squeeze from the biggest fall in advertising revenues for a decade,' she said. 'Now is not the time to impose a new, publicly funded service on a fragile and highly competitive market without being certain of the likely result.'
Channel 4, which runs youth channel E4, welcomed the delay.
However, BBC chairman Gavyn Davies said BBC 3 - which would have a programme budget of £97m - was key to the both the corporation's digital ambitions and those of the government. 'Without BBC 3, our digital proposition looks that much less compelling and analogue switch-off looks that much further off,' he said.
Jowell welcomed Davies' planned reform of the BBC's governors - which would see the secretary's office replaced with a new governance and accountability office and the recruitment of new advisors - saying it would help modernise the body for the 'new world the corporation faces'.
She also announced former Financial Times editor Richard Lambert would carry out the long-awaited review of the BBC's News 24 channel. Lambert is expected to report by the end of June.
Jowell faced fresh criticism in parliament this week after she announced a two-week delay for the publication of the draft communications bill. Originally expected in four weeks, it will now not be published until the end of April and will be followed by three months of further consultation. Tory media secretary Tim Yeo warned the timing put at risk the government's target for the bill to become law by next summer and he introduced his own bill in the House of Commons, as predicted by Broadcast in January (11.1.02).