title taken from book written by paul gilroy.

The full title of this book is: 'There Ain't No Black in the Union Jack: The Cultural Politics of Race and Nation'. In this book, the author demonstrates the enormous complexity of racial politics in britain today. Exploring the relationships between race, class, and nation as they have evolved over the past twenty years, he highlights racist attitudes that transcend the left-right political divide.

The 'union jack' is a nickname for the uk's national flag. Therefore, also a British racist slogan for saying that there should be no black people in the UK. Thus 'conservative say there ain't no black in the Union Jack' could be another way of saying that old school UK conservative racist politicians and their followers don't want any foreign elements in their country. (Thanks to Graham for providing this info).