Jose Mourinho
Under Mourinho, Chelsea dominated the Premier League last season and are yet to spend heavily in the transfer market.AFP

Jose Mourinho claims that Chelsea's rivals are trying to 'buy' the Premier League title and has backed his team to fight against such lavish spending in 2015/16 and reclaim their domestic crown.

With their last top-flight success having come during the reign of Carlo Ancelotti in 2010, the Blues dominated proceedings last season after sufficiently bolstering their squad and suffered just three defeats on their way to finishing eight points clear of nearest challengers Manchester City.

The costly acquisitions of Diego Costa and Cesc Fabregas were crucial to that impressive achievement, but Chelsea are yet to spend big in the current transfer window with Stoke City goalkeeper Asmir Begovic their most expensive recruit so far at a reported £8m ($12.4m).

By contrast, Manchester United are believed to have spent in excess of £70m on deals for Memphis Depay, Matteo Darmian, Morgan Schneiderlin and Bastian Schweinsteiger, while Manchester City have splashed almost £60m to sign Raheem Sterling, Fabian Delph, Patrick Roberts and Enes Unal.

Although perhaps still not considered as genuine title contenders owing to their disappointing absence from the top four last term, Liverpool have also been eager to strengthen. Roberto Firmino, Christian Benteke and Nathaniel Clyne stand out as the three most important of seven acquisitions at Anfield this summer to date.

Chelsea were often accused by envious rivals of using Roman Abramovich's significant financial backing to their advantage in the years that followed his purchase of the club in 2003, and Mourinho believes such an approach is now widespread.

"In the beginning of Mr Abramovich coming to Chelsea, Chelsea was buying the title," he was quoted as saying by Sky Sports after his side's penalty shootout victory over Paris Saint-Germain at the International Champions Cup last night.

"Now, they are buying the title. All of them, they are buying the title. It is up to us to be strong and to fight them and, obviously, to try and win it again, even without the big investments."

In addition to bringing in Begovic as a replacement for Petr Cech following the latter's move to Arsenal, Mourinho has also completed deals for young midfield pair Nathan and Danilo Pantic in recent weeks as well as bringing in former Manchester United striker Radamel Falcao on a season-long loan.

Chelsea drew 1-1 with Ligue 1 champions PSG at the Bank of America Stadium in Charlotte, North Carolina after an equaliser from Victor Moses cancelled out Zlatan Ibrahimovic's 24th-minute strike and Thibaut Courtois notched the decisive spot kick in a 6-5 penalty win.

They face Barcelona in Washington DC next, before returning to Stamford Bridge to face Fiorentina on 5 August.

Chelsea meet FA Cup holders Arsenal in the Community Shield at Wembley three days before that match and open their title defence at home to Garry Monk's Swansea City.