Steve Smith may be limited to playing in twenty20 competitions around the world during his exile from international cricket, but that hasn't stopped him from climbing back to the top of the international Test batting rankings.

Despite having not played a Test since March, the former Australian captain has returned to the top of the International Cricket Council [ICC] Test batting rankings ahead of India captain and arch-rival Virat Kohli.

ICC Test batting rankings 1. Steve Smith (AUS) - 929 2. Virat Kohli (IND) - 919 3. Joe Root (ENG) - 851 4. Kane Williamson (NZL) - 847 5. David Warner (AUS) - 820

Smith is currently serving a 12-month ban from international and state cricket for his role in the ball tampering scandal that engulfed Australian cricket during the third Test against South Africa in March.

Due to the way the ICC calculates its player rankings his score has not changed since that time, meaning he remains on top of the table owing to his stellar form with the bat before his ban.

Smith had been overtaken at the top of the rankings list last week by Kohli after he scored 149 and 51 in the first Test against England at Edgbaston earlier this month.

However, the Indian captain's tenure at the top of the rankings was short lived, after both he and his team capitulated in the second Test at Lords last week.

Kohli's scores of 23 and 17 in India's innings and 159 run defeat in that second Test meant that his ranking score fell by a sufficient amount for him to fall back to second spot.

The two rivals — who have clashed on the field in the past — have been denied an on-field reunion in Australia this summer due to Smith's ban.

Fellow Australian David Warner — who is also serving a suspension from international cricket after the ball tampering saga — is currently ranked in fifth spot behind Joe Root.

Uzman Khawaja is the highest ranked Australian in 19th spot.

Warner and Smith are the only two Australian batsmen ranked in the top ten. ( Reuters: Rogan Ward )

How are the rankings measured?

The ICC gives players a continuous rating based on their performance in Test matches using a points-based system that leads to "a sophisticated moving average".

Players are rated on a scale of 0 to 1000 points. If a player's performance improves on their past record, their points will increase but if the performance declines, the points tally will go down.

The score each player achieves is calculated using an algorithm based on "a series of pre-programmed calculations based on various circumstances in the match".

The algorithm ensures that there is no subjective assessment and no human intervention.

To appear on the list, players must have played in the format within a certain qualifying period.

For Test matches, this is between 12 and 15 months, meaning Smith and Warner's ranking is protected for the duration of their 12-month bans.