Parrikar was appointed by Goa Governor Mridula Sinha on Monday after he staked claim on Sunday to form the government.
The move came amid controversy and allegations of horse-trading and violation of constitutional norms and precedent by the Congress party, which had emerged as the single largest party with 17 seats in the 40-member assembly.
While the BJP won 13 seats in the February 4 elections, after votes were counted on Saturday (March 11), the saffron party leaders were quick off the block and garnered support of three MLAs each from the Maharashtrawadi Gomantak Party (MGP) and Goa Forward (GF) as well as two Independent legislators, before meeting the Governor.
One more Independent, Prasad Gaonkar from Sanguem constituency, joined the ruling coalition on Monday, taking its strength to 22, one more than the magic mark of 21 seats.
Sources in the Congress party told IANS on condition of anonymity, that the Congress leadership, which is being accused of acting sluggishly and thereby losing the opportunity to form the government, is now in contact with leaders from the MGP and GF, requesting them to switch over.
The Congress needs only four more MLAs to reach the crucial mark.
The floor test is expected to take place at 5 p.m., while the new legislators will be administered oath of office on Thursday morning.
Sinha on Sunday had granted Parrikar 15 days to prove his majority in the assembly, but the Supreme Court, which was hearing a petition filed by Congress legislative party leader Chandrakant Kavlekar, directed on Tuesday that the floor test should be held without delay on Thursday.