The Social Democrats (CSSD) have been running a campaign promising that ordinary people will not have to pay for the economic crisis, and that companies and the rich should be taxed to maintain a generous welfare system.
The latest initiative targets big companies, including Czech power firm CEZ and German power utilities E.ON and RWE.
Party chief Jiri Paroubek said that regardless of the economic crisis, profits at companies providing regulated services have been growing at the expense of customers, whose bills have been rising in recent years.
CEZ had record profit last year of 51.9 billion crowns ($2.75 billion), but it said the economic crisis and lower wholesale power prices would make this unsustainable.
"Electricity in the Czech Republic is more expensive than in Paris or London," Paroubek said. "In many cases these are companies with foreign owners, which transfer the entire profit abroad. The CSSD considers this trend unacceptable." Paroubek said that according to Austrian regulator E-Control and Czech statistical data, Czechs paid 18.95 euro cents per kilowatt hour, compared to 13.5 cents paid by an inhabitant of London.
He said the party would aim to cut or freeze prices to the level of "comparable European Union countries,” by boosting oversight bodies and performing an audit of regulated utility prices, among other things.
In targeting big firms and foreign investors, Paroubek is following the example of his political ally, leftist Slovak Prime Minister Robert Fico, who squeezed utilities after taking power in 2006. Paroubek said he would also look into banking fees and prices of telecommunication services.
The wholesale price of electricity is determined by the market. But the price paid by households is largely made up of fees for distribution, which are regulated by a state body.
The Czech Republic has had an interim cabinet led by non-affiliated Prime Minister Jan Fischer since the fall of a center-right cabinet in March 2009. The May 28-29 election will mark the end of his cabinet's term.
The Social Democrats lead the right-wing Civic Democrats by 5-13 points in opinion polls, but will almost surely fall short of an outright majority. In that case they may run a minority cabinet or form a coalition with the Civic Democrats or small centrist parties.
The Civic Democrats rejected the regulation plans.
"This is another clear signal to investors not to expect a reasonable outlook in the Czech Republic in the case of a CSSD victory," party chief Mirek Topolanek said.
The Social Democrats say that tax hikes and efficiency measures will allow the budget gap to be slashed to 3 percent of Gross Domestic Product by 2013 from 6.6 percent last year without cuts in welfare.
Analysts say whoever forms the next cabinet will have to make deep spending cuts and raise taxes to narrow the gap.
