Economic growth will slow in the second half of the year as the effect of improved confidence and better credit conditions starts to wear off, the CBI has predicted.

The business group said the recovery was "on solid ground" but expected expansion to ease to 0.7% in the third quarter and 0.6% in the final three months of the year, after growth of 0.8% in each of the first and second quarters.

It also warned of political risks including the possibility of a Scottish yes vote on independence – described as a "one-way ticket to uncertainty".

The CBI expressed concern about the possibility of a Labour government intervening in the energy sector and other markets if the part wins next year's general election. But it insisted it was non-party political and was also "not very keen" on the Conservatives' migration targets.

Its director general, John Cridland, said the possibility of a yes vote in the Scottish independence referendum was "the most important risk that the CBI and business are facing".

"The economic case for Scottish independence has not been made," he said. "Overwhelmingly, British business believes that the UK should stay together."

The CBI's deputy director general, Katja Hall, went one further, calling it "a one-way ticket to uncertainty and there is no return".

The CBI also increased its forecast for house price growth for this year to 9.5%, up from 3.5% in 2013, with a prediction of 5.3% for next year.

Its forecast for GDP growth for this year and next remained unchanged at 3% and 2.7%, respectively. The CBI said the recent period of accelerating growth would ease as the initial impact of business and consumer confidence, improving credit conditions and reductions in uncertainty started to wear off.

The slowdown also reflected weakness in productivity and wage growth, the CBI said, but added that it expected a gradual improvement, predicting average earnings to increase by 1% this year and by 2.4% in 2015.

Its view that signs of a pick-up in pay growth would be needed before any interest rate hike backed the stance of the Bank of England governor, Mark Carney, who led most of the rate-setting monetary policy committee in not voting for a rise last month.

Cridland also brushed off suggestions that Carney's apparent changes of tack on when rates would rise were confusing.

Cridland said: "The UK's recovery is on solid ground, with our quarterly growth on average outstripping G7 competitors over the last year. For the rest of the year, we expect growth to get onto a more even keel and the recovery to become further entrenched next year.

"Business investment has been growing better than expected so far this year, but it still has a lot of catching up to do to get back to its pre-crisis level.

"Although hundreds of thousands of new jobs are being created in the economy, there is little upward pressure on starter salaries outside a few hotspots, such as in parts of the IT sector.

"For longer-term staff though, awards are often a little higher. We expect wages to pick up across the board next year as the recovery continues."

A separate CBI survey showed economic growth slowed in the three months to August, with a five-month low of +21%.

Cridland said heightened tensions in Ukraine and the Middle East added to risks such as higher commodity prices and global market instability.

With party conference season approaching, he urged politicians in the UK "to focus on the UK's long-term economic security, not just on winning the political race".

Cridland urged parties to commit to adopting the outcome of the Davies commission on airport capacity, saying businesses were "not going to accept cherry-picking" of the proposals and wanted to see "diggers on the ground before 2020".

He said that as political positions of the major parties took shape ahead of the election there were "things in each of the emerging manifestos that we like and things that we don't like".

He added: "I think it's clear that business has some doubts about the Labour party proposals about intervening in markets.

"In response to public concern about the perceived failings of some markets – in financial services, in energy, in housing – we are seeing proposals from Labour to intervene more in markets than governments have for the past generation."

In another development, the CBI was also launching a "great business debate" to highlight the positive contribution made to society, as well as to answer public concerns on issues such as wages, diversity and tax contributions.