The British high commission says it is collating relevant information about some Nigerians who engaged in anti-democratic actions during the elections.
The commission said it was concerned by the use of inflammatory ethno-religious language by some political figures.
On March 18, the governorship and house of assembly elections were held in 28 states across the country.
House of assembly election was conducted in the remaining eight states.
In a statement released on Wednesday, the commission said members of its observation team witnessed vote buying, voter intimidation, destruction of election materials, and harassment of journalists during the governorship elections.
The commission said improvements were made in election logistics by the Independent National Electoral Commission (INEC) during the polls.
“We observed improvements around elections logistics by INEC during the gubernatorial elections, particularly when compared to the Presidential elections,” the statement reads.
“More polling units opened on time, there was greater evidence of BVAS and IREV working and results uploaded in real-time from polling units and collation centres. These are positive markers to build on for future elections.
“However, there were notable points of concern. Members of our observation mission personally observed violence, and voter suppression in numerous voting locations.
“We witnessed and received credible reports from other observer missions and civil society organisations, of vote buying and voter intimidation, the destruction and hijacking of election materials, and the general disruption of the process in numerous states including Lagos, Enugu, and Rivers.
“In addition, we observed incidents of harassment of journalists. Freedom of speech and a free press are crucial for a healthy democracy, and journalists must be able to go about their work without being threatened.
“The UK is concerned by the use of inflammatory ethno-religious language by some public and political figures.
“We call on all leaders not just to distance themselves from this kind of language, but to prevent those who speak on their behalf from doing so in this way.
“It is a testament to their commitment to democracy that many Nigerians were prepared to vote despite being faced with intimidation and hostility.
“The UK Minister of State for Development and Africa, Andrew Mitchell MP, said on 21 February, that the UK is prepared to take action against those who engage in or incite electoral violence and other anti-democratic behaviours, and action could include preventing people from obtaining UK visas or imposing sanctions under our human rights sanctions regime.
“We can confirm that we are collating relevant information, with a view to taking action against some individuals.”