The largest opposition party in Bulgaria, the Bulgarian Socialist Party, is likely to set out to revise the country's flat 10% corporate and income tax rates at a party congress next week, just months ahead of the upcoming general elections.

The Bulgarian Socialist Party (BSP), currently in opposition to the government of Prime Minister Boyko Borisov and the center-right GERB party, is set to host its 48th congress in order to approve the party's pre-elections framework and prepare for the upcoming parliamentary vote in June, MPs revealed on Friday.

Cancelling Bulgaria's flat-rate taxation and introducing higher taxes for the richer is expected to be one of the main messages that BSP would send out, although this is still in discussion as some members are "for", others "against". However, a year ago the BSP plenum did declare itself against the flat taxes in Bulgaria, which are often lauded by foreign investors.

Largely thanks to its flat 10% corporate and personal income tax rates, Bulgaria at present enjoys the lowest taxes in the European Union. Even though the flat taxes were adopted by the so called three-way coalition cabinet of Sergey Stanishev, BSP leader and current leader of the Party of European Socialists, it has been criticized on a regular basis by senior Socialist functionaries.

The Bulgarians Socialists are also said to be preparing to promise a considerable increase in retirement pensions – as far as 70-80%.

Reports say the main disputes among the Bulgarian Socialists are also centered around how many specific "messages" BSP's pre-elections framework will include; the framework itself will become the basis for the party's actual elections program.

Two documents have been prepared, one by party deputy chairperson Georgi Pirinski and one by executive bureau member Yanaki Stoilov, "Dnevnik" reported.

Stoilov's proposition contained many particular commitments, even in the first 100 days of the future government, whereas Pirinski's document included broader "messages", such as "free citizens", "fair state" and "social solidarity", MPs told.

At the end, party leaders decided to compile both and come up with only a few, clear messages.

Those will, most likely, include urges to "direct democracy", since BSP's leader Sergey Stanishev has spoken about a nationally-responsible government with active citizen-participation.

It is assumable, that if the BSP wins the elections, it will host more referendums, like the referendum on the construction of a second nuclear power plant that Bulgaria held on January 27, 2013. For example, about the heatlhcare reform, sources from the party's HQ shared.