Ed Miliband's Labour party has maintained its seven-point lead over the Conservatives according to the latest Opinium/Observer poll.

Despite a difficult period for the opposition with the chancellor, George Osborne, able to claim there are signs of improvement in the state of the British economy, Labour now stands at 37%, two points up from a fortnight ago. The Tories have also gone up two points to 30%. The Liberal Democrats remain on 8%.

The losers since the last poll appear to be Nigel Farage's Ukip who stand at 16% – a drop of three points.

The failure of the Tories to pin back Labour's lead will worry their party strategists given an improved perception of their handling of the economic levers.

Asked who they trusted more to handle the economy, 32% said David Cameron and Osborne, a 4% rise since the question was asked in June. Worryingly for Labour only 21% backed Miliband and Ed Balls, the shadow chancellor, the same as six months ago.

In June polling showed that just 9% thought the UK economy was in good shape. Photograph: Observer

In June polling showed that just 9% thought the UK economy was in good shape. That figure has gone up to 17%.

And more people now say the state of the economy is due to the current coalition government, with this movement most likely due to Conservative voters crediting positive economic news to the government, the polling suggests. One in five (22%) Conservative voters say the coalition is responsible for the current state of the economy, up from 8% in June.

Yet an increased confidence in the economy and a sense that the coalition has done some good things does not appear to be feeding into the headline polls. The new poll shows that all four of the main parties are within two percentage points of where they were at this point in 2012.

• This article was amended on 15 December 2013. The original headline and first paragraph wrongly suggested Labour's lead over the Conservatives was two points, rather than seven.