McLaren's Lewis Hamilton has asked stewards at this week's Monaco Grand Prix to keep a close eye on the Toro Rosso drivers after accusing them of helping title rival Sebastian Vettel at the previous round in Spain.
World champion Vettel's Red Bull and Italian-based Toro Rosso are sister teams, although independently run.
Hamilton complained after the Spanish Grand Prix last weekend that Switzerland's Sebastien Buemi and Spaniard Jaime Alguersuari had held him up while he chased eventual race winner Vettel.
The 2008 world champion has asked stewards to consider imposing penalties, but
Red Bull's team boss Christian Horner scoffed at Hamilton's concerns.
The Red Bull and McLaren drivers lapped all the others in Barcelona, but overtaking is notoriously difficult round the narrow streets of Monaco.