The 25-year-old tested positive for a banned substance and was sent home from the tour of New Zealand last week.
Sports Minister Dayasiri Jayasekera told parliament that authorities will send a B sample to the International Cricket Council for testing.
"We are doing all we can to defend him," said the minister.
"We are wondering if this allegation is a conspiracy to keep him out of next year's T20 World Cup."
Jayasekera added that Sri Lanka President Maithripala Sirisena had spoken to Perera, who was withdrawn from the series in New Zealand which comprises two Tests, five one-day internationals and two Twenty20 internationals.
Sri Lanka are defending champions for next year's ICC World Twenty20 in India in March and April, and will face England, South Africa, West Indies and a qualifying nation in the group stage.
Kusal Perera's failed drugs test could be part of a "conspiracy" against the wicketkeeper-batsman, according to Sri Lanka's sports minister.