Iga Swiatek has cast aside her doping saga to launch her summer campaign in explosive fashion at the United Cup in Sydney.

The world No.2 crushed lowly-ranked Malene Helgo 6-1 6-0 in barely an hour, then teamed with Jan Zielinski to win a thrilling deciding mixed doubles rubber to pilot Poland to a 2-1 victory over Norway on Monday night.

Casper Ruud had levelled the tie for Norway with a 7-5 6-3 win over Hubert Hurkacz in the men's match but nothing could take the shine off Swiatek's eye-catching double act.

The five-time grand slam champion was playing her first official matches since a one-month suspension late last year after returning a positive test for the angina medication trimetazidine, which the International Tennis Integrity Agency (ITIA) accepted was caused by contamination of a medicine she was taking for jet lag.

While saying on arrival in Australia that she had expected more negative reaction to her plight, Swiatek has come under fire from players including Novak Djokovic and Nick Kyrgios in recent days.

Kyrgios claimed the bans of Swiatek and men's world No.1 Jannik Sinner for taking prohibited substances were "disgusting" for tennis, while Djokovic agreed they were "not a good image" for the sport.

But if Swiatek has even heard of the remarks, she didn't seemed fazed on court in her first outings of the summer.

The former world No.1 broke the 404th-ranked Helgo five times, won 88 per cent of points after landing her first serve and clubbed 24 winners to more than offset eight unforced errors.

No wonder Swiatek said she was happy with "everything" in her game after receiving a rousing ovation from the crowd at Ken Rosewall Arena.

"I'm happy for sure with the performance. It's not easy to play for your country sometimes - the pressure is a bit bigger," she said.

"But I'm really excited. Every year I feel like I can really take so much energy from that and also from the people, from the fans.

"I feel good. I feel happy for sure. I'm happy that I can play tennis overall."

After losing to Czechia in their opening tie, Ruud and Ulrikke Eikeri had to beat Swiatek and Zielinski in the mixed to stay in the hunt for a quarter-final berth.

Instead Poland are now in pole position to top the group and advance after Swiatek and Zielinski recovered from a mini break down in the match tiebreaker to prevail 6-3 0-6 10-8.