diff --git a/ably/auth.go b/ably/auth.go
index 1b0dc1b0..56d1a309 100644
--- a/ably/auth.go
+++ b/ably/auth.go
@@ -545,7 +545,7 @@ func detectAuthMethod(opts *clientOptions) (int, error) {
 	if !isKeyValid {
 		return 0, newError(ErrInvalidCredential, errInvalidKey)
 	}
-	if opts.NoTLS {
+	if opts.NoTLS && !opts.InsecureAllowBasicAuthWithoutTLS {
 		return 0, newError(ErrInvalidUseOfBasicAuthOverNonTLSTransport, errInsecureBasicAuth)
 	}
 	return authBasic, nil
diff --git a/ably/options.go b/ably/options.go
index 1bf26783..6c7c8362 100644
--- a/ably/options.go
+++ b/ably/options.go
@@ -408,6 +408,10 @@ type clientOptions struct {
 	// LogHandler controls the log output of the library. This is a function to handle each line of log output.
 	// platform specific (TO3c)
 	LogHandler Logger
+
+	// InsecureAllowBasicAuthWithoutTLS permits an API key to be used even if the connection
+	// will not use TLS, something which would otherwise not be permitted for security reasons.
+	InsecureAllowBasicAuthWithoutTLS bool
 }
 
 func (opts *clientOptions) validate() error {
@@ -1316,6 +1320,14 @@ func WithDial(dial func(protocol string, u *url.URL, timeout time.Duration) (con
 	}
 }
 
+// WithInsecureAllowBasicAuthWithoutTLS permits an API key to be used even if the connection
+// will not use TLS, something which would otherwise not be permitted for security reasons.
+func WithInsecureAllowBasicAuthWithoutTLS() ClientOption {
+	return func(opts *clientOptions) {
+		opts.InsecureAllowBasicAuthWithoutTLS = true
+	}
+}
+
 func applyOptionsWithDefaults(opts ...ClientOption) *clientOptions {
 	to := defaultOptions
 	// No need to set hosts by default
diff --git a/ably/options_test.go b/ably/options_test.go
index 855076bd..cc86e794 100644
--- a/ably/options_test.go
+++ b/ably/options_test.go
@@ -236,6 +236,28 @@ func TestScopeParams(t *testing.T) {
 	})
 }
 
+func TestOption_NoTLS(t *testing.T) {
+	t.Run("does not allow basic auth with no TLS", func(t *testing.T) {
+		_, err := ably.NewREST(
+			ably.WithKey("xxxxxx.yyyyyy:zzzzzz"),
+			ably.WithTLS(false),
+		)
+		assert.Error(t, err)
+		errInfo, ok := err.(*ably.ErrorInfo)
+		assert.True(t, ok)
+		assert.Equal(t, errInfo.Code, ably.ErrInvalidUseOfBasicAuthOverNonTLSTransport)
+	})
+
+	t.Run("allows basic auth with no TLS when InsecureAllowBasicAuthWithoutTLS is set", func(t *testing.T) {
+		_, err := ably.NewREST(
+			ably.WithKey("xxxxxx.yyyyyy:zzzzzz"),
+			ably.WithTLS(false),
+			ably.WithInsecureAllowBasicAuthWithoutTLS(),
+		)
+		assert.NoError(t, err)
+	})
+}
+
 func TestPaginateParams(t *testing.T) {
 	t.Run("returns nil with no values", func(t *testing.T) {