The perception of the federal Liberals and their leader, Justin Trudeau, rose favourably over the summer and they continue to ride high on the Nanos Party Power Index.

The Liberals continue to trend up on the Index and now have an 11-point advantage, according to the latest data released Wednesday. The Liberals currently stand at 60.7 points out of 100 on the Index, followed by the NDP at 50.2 points, the Conservatives at 49.5 points and the Green Party at 31.5 points.

The Liberals are up 5.2 points compared to May 30, while the NDP are up 2.3 points. The Conservatives are down 3.0 points, while the Greens are down by 1.3.

The Party Power Index is a basket of political goods that rolls up ballot support, accessible voters, preferred prime minister and leader evaluations.

Meanwhile, Trudeau continues to enjoy a lead over Prime Minister Stephen Harper on the preferred prime minister measure. Back on May 30, 32.4 per cent of Canadians said Harper was their preferred choice for prime minister, followed by Trudeau at 29.7 per cent, NDP Leader Thomas Mulcair at 15.0 per cent, and Green Party Leader Elizabeth May at 5.7 per cent.

According to the data released Wednesday, Trudeau now has a seven-point lead over Harper on the preferred prime minister measure. Currently, 35.2 per cent of Canadians prefer Trudeau as prime minister, 28.2 per cent prefer Harper, and 17.6 per cent prefer Mulcair. Green Party Leader Elizabeth May trails at 3.1 per cent.

The Nanos Party Power Index is based on random telephone surveys of both cell and land lines with 1,000 Canadians, using a four-week rolling average of 250 respondents each week. The survey is considered accurate within 3.1 percentage points, 19 times out of 20.