Officer numbers in fell below this figure for ten out of the 13 weeks in the past three months, according to figures obtained by the Sun newspaper.
The force say that there are always "fluctuations" in numbers but the important measure is at the end of the quarter.
But Labour justice spokeswoman Clare Baker said: "These are incredibly serious allegations. Michael Matheson should be explaining this to Parliament as a matter of urgency.
"People are sick of statistics being spun when they see the reality in their own communities - a police force facing huge cuts from the SNP Government in Edinburgh.
"It would be completely unacceptable If official statistics have been manipulated to get the SNP out of jail on police cuts"
The figures for this year appear to show a pattern of decline in the build-up to the week when quarterly figures were made public in June and September. At this stage they spike above the 17,234 target level, prompting claims that Police Scotland is "rushing recruits" onto the books to boost numbers.
A Police Scotland spokesman said: “Officer numbers are formally reported quarterly. Returns to date confirm a quarterly strength above 17,234.
“There will be weekly fluctuations in numbers as a result of monthly retiral patterns, but we continue to recruit with an intake of 150 last month and further intakes planned.”