By Gabriela Baczynska and Pawel Sobczak
WARSAW (Reuters) - Polish Prime Minister Donald Tusk's centre-right ruling party was on course to win a parliamentary election Sunday, an exit poll showed, paving the way for four more years of cautious economic reforms.
The exit poll, published after voting ended, showed Tusk's pro-business Civic Platform winning 39.6 percent, short of an absolute majority but comfortably ahead of Jaroslaw Kaczynski's nationalist-conservative Law and Justice party on 30.1 percent.
The scale of the victory, if confirmed, would give Tusk enough support to renew his alliance with the Peasants' Party, his junior coalition partner for the past four years.
Tusk smiled broadly at his party headquarters and held a bouquet of flowers above his head.
Financial markets are expected to welcome the result, which points to four more years of relative political and economic stability in the European Union's largest eastern member state at a time of crisis in the euro zone.
The post-communist Democratic Left Alliance won 7.7 percent, the rural-based Peasants' Party 8.2 percent, and a new liberal grouping called Palikot's Movement 10.1 percent, the exit poll showed.
The result is a personal triumph for Tusk, 54, a pragmatic liberal conservative whose party would be the first to win re-election since the end of communist rule in 1989 in the country of 38 million people.
Tusk now needs to tackle Poland's large budget deficit, set to reach 5.6 percent of gross national product (GDP) this year, and to rein in public debt, seen at 53.8 percent of GDP, or face the risk of Poland being downgraded by ratings agencies.
He is expected to ask the Peasants' Party to recreate the coalition that oversaw four years of strong economic growth and steered Poland smoothly through the 2008-09 global crisis.
He also favours closer integration with the rest of the European Union.
Kaczynski's calls for a halt to privatisation, for higher taxes on the wealthy and for a more combative stance in dealings with Poland's EU partners had unsettled investors.
A government led by Kaczynski, 62, would have been likely to might strain Poland's relations with its two large neighbours, Russia and Germany, as happened when it was last in power from 2005 to 2007.
Kaczynski distrusts both Berlin and Moscow -- Poland was carved up under a Nazi-Soviet pact before World War Two -- and raised eyebrows during the election campaign by repeating in a new book his view that Berlin is trying to subdue Poland.
Tusk has good personal ties with German Chancellor Angela Merkel and has maintained a cautious rapprochement with Moscow, despite strains over a plane crash last year that killed then-President Lech Kaczynski, Jaroslaw Kaczynski's twin.
(Writing by Gareth Jones, editing by Timothy Heritage)
